RED 15w droppng connection all the time after upgrade to 18.5.4 and 3.0.008

There is a ticket open with support and they are looking into it.

Was anything determined?

Unfortunately support were requiring us to carry out all sorts of log captures on the RED and the Firewall. The issue didn't occur all the time so to have a tech onsite for a day and impact the client were not financially viable
The RED15w is completely stable with compression turned off, so that is what we have done for now.

Your findings were helpful.  Turning off compression seems to also resolve RED stability issues here affecting a couple XG's on SFOS 19.0.1 MR-1-Build365 and RED 3.008:

XG210 rev3 "Firewall RED Client" <<-- >> XG330 rev2 "Firewall RED Server"

XG115w rev2 "Firewall RED Client" << -- >> XG330 rev2 "Firewall RED Server"

The problem began after updating from SFOS 18.5 and previous RED versions.  I haven't done inventory here of RED versions on other XG's for a comparison so there may still be more factors to consider.

Your findings were helpful.  Turning off compression seems to also resolve RED stability issues here affecting a couple XG's on SFOS 19.0.1 MR-1-Build365 and RED 3.008:

XG210 rev3 "Firewall RED Client" <<-- >> XG330 rev2 "Firewall RED Server"

XG115w rev2 "Firewall RED Client" << -- >> XG330 rev2 "Firewall RED Server"

The problem began after updating from SFOS 18.5 and previous RED versions.  I haven't done inventory here of RED versions on other XG's for a comparison so there may still be more factors to consider.