pt-online-schema-change -- can't get it to stop quitting w/ "Threads_running=108 exceeds its critical threshold 100"

I've got an InnoDB table over 50GB with indexes. The query I'm running looks like this: pt-online-schema-change h=localhost,D=db,t=table --critical-load="Threads_running=100" --check-slave-lag "h=XX.XX.XX.XX" --max-lag 10 --execute --pass PASS --alter "REORGANIZE PARTITION max INTO ( PARTITION p19 VALUES LESS THAN ( UNIX_TIMESTAMP('2016-05-01 00:00:00') ), PARTITION p20 VALUES LESS THAN ( UNIX_TIMESTAMP('2016-06-01 00:00:00') ), PARTITION max VALUES LESS THAN maxvalue )" No matter what settings I use, I get the Threads_running issue. I have also tried: --chunk-size 100 (also tried 20) --max-load="Threads_running=20" Shouldn't it just wait until threads running gets lowered? Why does it keep quitting? I could raise the critical load to allow 200 threads, but I'm afraid of the server crashing. Any advice?