Of course it has nothing to do with the programs, it is your setup.
I just looked into the first debug output and it reveals that you always used 4 threads/cores for all engines.
If I assume you just have a quadcore you already have the faulty setup.
While it is true that you used ponder off, you did not care about the OS,the GUI and probably other processes
running on your machine.
The usual thumb of rule is to leave one thread/core for other tasks and the OS.
Try to run the same thing with 2 threads per engine and report again
BTW for the future it would be much better and helpful to immediately report exactly
what you did and what your setup was, otherwise no one will take those 'bug' reports
And of course you should not open an 'issue'
at a random github account just because
you had no idea what happened.
Hopefully this doesn't sound too rude, but actually all I said should be common sense
at least for someone being here for so long.
Moreover you should try to ask first an expert before filing an issue, which in case of ChessGUI
clearly would be Graham (are there others?)