Are you sure that failures are because of RUM iniection? RUM is catching all exceptions in console log, because of that DT can show you whole exception messages. Such exceptions are thrown than by dtjsagent again so sometimes it looks like agent is source of errors true stack trace is from the moment when other JS file starts. It is possible that even without JS agent you had those errors but you didn't know. If this is incidentally not constant, it looks like what I said.
Signailir should be transparent for agent, you will se loading of this file, errors but nothing more as I know.
After disabling the RUM we haven’t seen these 500 errors but when we enabled it back they occur intermittently.
We have single tenant for multiple environments including both prod and test environments. Is it possible to exclude the RUM monitoring for the signalR only for a specific process groups rather than global?