We are having similar troubles with 14 Teamwork projects. Spinning wheel, slow send-receive, slow to open file, some crashing & frequent "offline" messages.
If anyone has info here it would be great. We can't confidently move our whole office to 14 if Teamwork is like this. Oddly, by comparison 13 Teamwork seemed very fast with the same files before migrating to 14. We have ditched all older libraries and embedded parts that could be upgraded to the 14 library.
matt johnson
archicad since 2004
imac 27, 4.2 GHz Intel i7, 16 GB RAM, radeon 575 4 GB, macOS 10.14.6
imac, 4.0ghz i7, 16gb ram, Radeon M9 390 2GB, OS X El Capitan