If you have shared array buffer when you activate web isolation, but not when you do not activate web isolation and use the shared array buffer OT, this confirm that your origin trial for shared array buffer is invalid.
An origin trial works for a specific domain / host name, and for a certain period. You should verify your current OT whether it applies to the correct host and is still valid (not ended). In all case, it’s probably easier to just re-create a token for this origin trial (with the expected host name), replace & test again with only the shared array buffer origin trial without web isolation. I don’t see any (obvious) reason for that not to work.
I suspect that your generated your shared array buffer origin trial before they extends the date to July 2022 (due to recent decision) and therefore, unless you renewed in between, the original date was until the end of Chrome 92.
Please renew it, and the validity / working period would be up to July 2022 for your new token.
