@techee I don't know if it's related at all, or if it could help in any way, but Chrome had a similar issue where it would open a new instance: "LaunchServices tries to open a second instance of Chromium". They committed a change with an attempt to fix this:
https://chromium.googlesource.com/chromium/src.git/+/fe15df9c055bb0c48e94aa9...