Yes, I just went back to examine older log files but that query isn’t new and is occurring for at least 6 months now as it turns out. I tried running the query multiple times right after each other manually myself without any issues trough Robo3T.
There are 778 users in total but definitely not all are active. When someone registers on our site he/she automatically gets access to this channel.
I now have a script in place that monitors the load of node and restarts rocket chat if the load is above a certain threshold for a certain of minutes but this is merely a workaround off-course.