I think the way the Hubitat skill is setup in Alexa you can only connect it to one hub at a time.
Sounds like the Alexa app on the remote hub is still installed and trying to connect. You should disable or delete the app. Its constant reconnection attempts may be gumming up the hubs memory.
Speaking of which, you may also want to try to "clean" the database by downloading a local backup then restoring it right away. This has been shown to fix rapid memory decline issue with 2.3.6 firmware, which would cause the hub to eventually crash. It is explained here: ‼ READ FIRST - Before Posting in Get Help
