VNC Server, Avalanche, Edit and clipboard

Scenario: (all using 5.28 on Raspbery Pi)

SCSI SSD on RasPi_A is shared unprotected
Avalanche 0.26 on RasPi_B has window open to VNC Server 0.21 on RasPi_A
User on RasPi_B uses !Edit to open shared file on RasPi_A …
… selects text
… and types Ctrl-C

Sometimes this is OK …
… but occaisionally, Avalanche on RasPi-B crashes …
… and user on RasPi_B is given error box, saying Data Transfer Failed

The !Edit window on RasPi_B remains open and can be further edited and saved.

VNC_Server on RasPi_A seems blissfully unaware of anything.