I have to UP this, as I’m having the same issue currently, and this is the only post I found about it, but nobody provided a solution.
I also have a grid, which has a link in a field, to a form.
When I make the form open in a new window, it works perfectly, but if I choose to open it as modal (in the Link properties), the form would open correclty, but all of its master details won’t work.
The master/details of the form only work If I navigate to the next element, then they start loading correctly!
So this happens only on the first load of the modal, once I click my link in the grid.
I assume this is a bug, as I tried creating new form with a single master/details, and using them when clicking the link, but as soon as I set the link property to “modal” , then when the form opens in a modal, its master/details part won’t be working