Tabs from some sites duplicate when clicked in FF 151.0.3 (64-bit)

This is true particularly with ChatGPT and Claude, but has happened on other tabs in the past couple of days. When I am on a different tab, and I click on a "problem" tab to view that content- it duplicates the tab instantly. If I click on "x" to close it, it duplicates again. I can close with Ctrl-W. It seems like certain tabs are "magic" tabs, because sometimes I can click the "x" to close a duplicate tab without issue. But when I go back to the original problem tab- the behavior persists. I don't really want to purge the cache for these sites, but I will if I have to. I had installed a new extension (TamperMonkey) a few weeks ago, but everything seemed fine until a couple days ago. I disabled that extension yesterday, but the problem persists. This problem existed before the latest Firefox update. I went to check the previous version number before posting (I update frequently) and it updated today. Thank you for your help! Bill