Hidden Google Sheets startup scripts?

I have a Google Sheet which is becoming unresponsive on startup for 2-3 minutes. I have disabled all formulas and scripts and the freezing actually starts AFTER the "calculating formulas" loading bar (top-right) finishes. Is it possible that somebody has hidden a script ? How can I find it ? Shouldn't all scripting projects be visible to everyone ? Could the hidden script come from an add-on someone installed ?

Some background info:

1. I noticed that copies don't not have the issue, so the culprit is something that does not get copied over when making a copy (ex: triggers). There are no third party apps using it that I know of , since nobody in the company codes in apps script (except me) so it's not like that sheet is being used somewhere and the copy not.

2. on one account it loads fast now (after I toggled make available offline on/off - now it's off. On all other accounts it's slow.)

3. Also it looks like a front-end javascript error, not a loading error since the tab simply becomes unresponsive.

4. On view only accounts the issue is also not present.

   Update: #2 worked so far on two accounts but it seems a bit scary to use this since we're afraid data might become out of sync..

According to the comments I received all bound scripts should be visible in the scripts.google.com > executions and there is no way to track any 3rd party apps using the sheet. Since disabling formulas and scripts didn't help my solution was to just make a copy. I am guessing that the huge "version history" is the culprit, especially because the unresponsiveness started soon after Google published it's "cell history" feature.