I have just updated to v0.12 and run the binary directly (with a diy systemd unit).
I had v0.11 working for a while, but after updating it seems that the modal dialogs stay invisible after opening.

I found, that they use the bootstrap .fade class for a transition, but the required .show class never gets attached.
So they keep opacity: 0 and are rendered invisibly in front of the page (you can see by the scrollbars going away from the .modal-open class on body which makes the overflow hidden).

I have attached a screenshot from developer tools.