Erlang/OTP-22 (released last year) introduced TLS distribution optimizations and message fragmentation which sound very related to the problem you saw:
The fragmentation in particular addresses the problem where a large message would block all other messages, including heartbeats, and cause nodes to look “down” when they’re not.
fantastic. thank you for sharing that -- my anecdote about this problem is slightly dated -- it would have been late 2017 early 2018 we were seeing the issue, which indeed predates OTP 22 release.
http://blog.erlang.org/OTP-22-Highlights/
The fragmentation in particular addresses the problem where a large message would block all other messages, including heartbeats, and cause nodes to look “down” when they’re not.