In the 1.67 version released today, there is a regression bug. When clicking on a blueprint slot to buy it, an error pops up.
Error message:
Assertion failure:…\src\GUI_SlotPlacer.cpp 111 - Error: [Unknown error]
After closing the error message, everything works fine, the slot is placed.
Addendum: no bug when buying Research Office (not tested for other facilities).