You are most likely not running R80 as this was not a gateway version, but actually R80.10 as suggested by the patch you mention.
The behavior suggests an issue negotiating HTTPS connections.
Log entries related to this might be there (particularly if HTTPS Inspection is enabled)--I would look for these.
tcpdumps of connections might also be interesting to look at.
Most likely to troubleshoot this much further, you're going to need assistance from the TAC.
Especially if they advised you to apply said patch and it didn't resolve the issue.