SIMBL Agent causing continuous crashes

I'm seeing a continous crash state involving the "SIMBL Agent_2019-2019-11-09" process that's gobbling up a lot of CPU time and slowing my iMac down. I can't find a running task called SIMBL in Activity Monitor (seeing All Processes). I can't find anything on my hard drive by that name except for a text file with a few lines of content going back to 2011. ReportCrash is running a process for each logged in account apparently involving the SIMBL agent crashing.

Example from Console:

default 17:34:53.191503-0800 ReportCrash Parsing corpse data for process SIMBL Agent [pid 74049]

default 17:34:54.588454-0800 ReportCrash Saved crash report for SIMBL Agent[74049] version 0.9.7 (0.9.7) to SIMBL Agent_2019-11-09-173454_Family-iMac-II.crash

default 17:34:54.591756-0800 ReportCrash Removing excessive log: SIMBL Agent_2019-11-09-173454_Family-iMac-II.crash

default 17:35:03.248459-0800 ReportCrash Parsing corpse data for process SIMBL Agent [pid 74060]

default 17:35:04.835130-0800 ReportCrash Saved crash report for SIMBL Agent[74060] version 0.9.7 (0.9.7) to SIMBL Agent_2019-11-09-173504_Family-iMac-II.crash

default 17:35:04.838654-0800 ReportCrash Removing excessive log: SIMBL Agent_2019-11-09-173504_Family-iMac-II.crash

I can't find the PIDs called out in the Console log in Activity Monitor. Very frustrating.

I obviously want to stop this. Anyone have some insight what process is actually causing this & how to make it stop? I'll keep investigating.

Thanks!