sponge version: spongeforge-1.12.2-2838-7.1.7-RC3843.jar

heapdump and heapsummary command can cause servers to lag and all players disconnect.
About 30 players.
I'm afraid to analyze heap now

You need to freeze the JVM to take a heap dump. If you didn't, the contents of the heap would be constantly changing while you were trying to capture it and you wouldn't get a useful result.

Nothing spark can do to combat this unfortunately.