Construction loan - Ex-partner does not pay his share

By the way, a judicial dunning procedure is also possible. If she doesn't respond again, the amounts will be acknowledged...

Oh yes, that's right. You can also get an enforceable title there, and if she just waits everything out and simply doesn't take care of it, it doesn’t even take long. Anyone who doesn’t file an objection is quickly "due".

Going straight through a notary lawyer will work, so he should just do it now; everything else will cost him more money but above all your nerves.
The house sale is off the table, since split into 2 condos, mutual consent on both sides is not to be expected.

Measured against the expected duration of this dispute and its possibly fatal burdens also for your relationship, if I were him I would cover these €30,000 and trust that in the case of inheritance it will ultimately end up with my children.
It’s about an emotional conflict and as long as a connection between the ex-spouses exists, this tug-of-war will continue on all still connected levels.
Your partner should now make up the decisions deferred back then, even if they are painful. A real separation only happens when there are no longer any possibilities to influence the other. He has done his part by signing and bears his share of today’s dilemma.
My advice to you would be to stay completely out of it; I also wanted nothing to do with this annoyance, whose solution path your partner obviously chooses entirely on his own and therefore should bear completely alone. He has his share in causing it to come to this and as long as this relationship is not completely separated such tugging will be possible.
Going through such brutal stress for €30,000 and taking it into my new life would be out of the question for me. I could jump over this hurdle, right or wrong, to finally have more peace again, especially for you/you all; it "only" costs 30K.
I would immediately transfer the apartment to my children because I no longer want this still existing connection and would therefore keep them completely out of my new life. Joint ownership always connects; you have to discuss things, problems with tenants, decide together and that for a lifetime. Does he actually want that?
If he does not clearly separate it now again, it will keep coming up again and again for the next 20 years and accompany you permanently.
For 30K, I would buy my freedom, albeit belatedly; my lifetime and my peace are far too precious for that.
I know what I am talking about, so this is my opinion about this situation. In this case, his lasting freedom and less stress, also for your life, simply costs him money, and with 30K I would find this option even quite cheap.
Hoping it will resolve differently can become very expensive financially and emotionally and above all you are already paying a high price for it at the moment, as can be seen while reading. I am thinking of your beautiful meadow and the lovely house on it...... he should end this thing finally so that you can enjoy it again instead of endlessly tugging at this old relationship. Every day is one too many!
The worst case is by no means reached yet. Just imagine the new boyfriend of the ex-wife moves in there and deliberately parks his Opel Manta in the wrong parking space, does this or that to show that HE is now there....... this connection must be severed or you will continue to have "fun."

By the way, there are also people who need such drama. One should not forget that. Otherwise, they wouldn't know what else to do.

Exactly, he has paid the entire 550 € so far. At the time of the loan agreement, she said she wanted to pay her 30,000 euros from the inheritance from her mother (who is still alive).
At the divorce (11/19) it was then agreed that each should take over the installment of 275 €, but he continued to pay the 550 euros alone for the time being, only she has been refusing to sign the SEPA direct debit mandate for her 275 euros for months...

Okay, in this case it already becomes clear why the bank feels no pressure. They get their money first anyway. This is also better for your husband at first, because it doesn’t seem to be his wish to see the house at auction.
According to your description, he has the claims against his ex, so he has to assert them if he wants the money. Legally, it would be his right.
You can also handle this yourself with people who try to "sit it out" without a lawyer. The procedure is described a lot on the internet. Basically, he has to demand the owed money from her (should be several thousand by now?) by registered mail with a reasonable deadline. If she doesn’t pay / ignores it, for safety send another registered mail setting a grace period and announcing the reminder procedure. If she refuses that too, initiate court-issued dunning proceedings. You can do that yourself at the local court, also online.
There are then two possibilities: Either she objects – but if the facts are really as you present them, that wouldn’t be very smart of her. Then it would go into an actual procedure as far as I know. She would then also have to prove that she is not obliged to pay.
Or she doesn’t object. Then your partner has an enforceable title in hand afterwards.

What I would only secure beforehand is that there is no (written?) agreement that she pays her share of the 30,000, for example, only in one lump sum after X years, or something similar. Ideally, you would have something in writing saying that both parties have to pay regular installments of 275 €.

But all this would basically only be the more stressful way to get his rights if the bank refuses the splitting of the loan. That option doesn’t seem to be off the table yet. That would be optimal for you, because then your partner would be off the hook and his ex can do whatever she wants with her own loan of 30,000.

OMG I already wrote upfront that he should service the loan and obtain a title and was virtually stoned for it! Morals etc... But still the right way if you have nothing to give away! What I don’t quite understand now is that you speak upfront of a [Grundschuld] on the house but suddenly about leasing and consumer credit. Which is possibly an important difference!

OMG I already wrote earlier that he should service the loan and obtain a title and I was virtually stoned for that! Morals etc... But still the right way if you have nothing to give away! What I don’t quite understand now is that you talk about a land charge on the house at the beginning but suddenly about leasing and consumer credit. Which is perhaps an important difference!

she probably isn’t told the truth. only his version