I am having the same problem in 1.14.1 repeat command blocks are not updating, they worked perfectly in 1.14 but 1.14.1 it is hit and miss sometimes they update and then other times they don't, I hope they fix this because I can't see how I can continue making maps when the commands don't even work..
I have the same problem when I try to load a world in 1.14 Pre-Release1, the game crashes and I get this error log, Error: java.lang.IllegalStateException: POI data mismatch: already registered at ev{x=1195, y=79, z=1887}
all worked fine with the last snapshot until this update, I hope it is not because of some 1.13 villagers I have in my world, since all the villagers have been updated now...
This bug about villagers closing Gui's, has not been fixed in the latest snapshot 1.14.4 pre-release 6, hopefully it will be fixed soon.