Must wait a long time after operation to avoid index.lock file conflict

Since a recent update (a few months) I have been getting index.lock errors like below when I perform one operation (pull, commit, merge) then wait a few seconds after it appears complete (but there is still a spinner in the upper portion of the log view) then do a second operation (even add a change to the index). Frequently I have to have sourcetree fetch then wait for all the spinners to stop to get sourcetree to perform any git operations again. This is horrendous for my productivity since I like to view diffs and stage hunks in the UI but each change requires this long delay.

For full disclosure I have 2 clones of the same stash repo and usually have a sourcetree window open for each. I also have a fetch all bash script I run frequently to get all changes on the repo in all my clones (fetch clone 1, fetch with tags clone 1, fetch clone 2, fetch with tags clone 2). Running or not running this script has not seemed to affect sourcetree's behavior and I have been seriously considering not using or recommending it since it performance overall and this issue mean it is nearly unusable now.

"fatal: Unable to create '/Users/robertm/stash/monoceros_MERGE/.git/index.lock': File exists.

If no other git process is currently running, this probably means a
git process crashed in this repository earlier. Make sure no other git
process is running and remove the file manually to continue."