Using Mac OS X 12.6.8 and Remote Desktop 10.9.2. Beginning two versions back (10.9.0?), copy and paste works for a while after launching RD, but it eventually fails when copying from the remote mach...
I'm finding now that only some Mac applications get the spinning beach ball whereas others keep working. Slack is the biggest culprit. Simply clicking on the Slack application after having been using RDC will trigger the beach ball for a minute or two. While that's happening, I can usually use Chrome or other apps on my Mac. RDC also remains usable during this time.
I'm now using RDC 10.9.5 (2179) and the latest Slack app (4.36.136) and it keeps happening at least once per day when switching from RDC to Slack, whether or not I've explicitly just copied something or not from within the RDC client.