"This page was reloaded because of a problem" on every page when using latest Safari extension

I've been running into this issue since mid-February. I'm using 1P8 (latest beta) and https://apps.apple.com/us/app/1password-for-safari/id1569813296?mt=12 with Safari Technology Preview [Release 140 (Safari 15.4, WebKit 17614.1.1.5)]. This issue is specific to the pairing of Safari (or STP) with the external 1Password for Safari browser extension.

Typically, it will first crash the tab and report that "the webpage reloaded because an error occurred", then will subsequently (and sometimes automatically) perma-crash the tab (i.e., Safari will stop bothering to try) and report "A problem repeatedly occurred with {URL}." It happens in cases where the username/password field shows the 1P prompt with the list of credentials. As soon as you select a credential, the browser process crashes.

The biggest frustration for me is Okta (used for work, which means I get aggressively logged-out), but I'd estimate it happens on probably 90%+ my login attempts (which is different from the number of unique websites I visit). Generic Apple Support Community links will not be helpful as it is clearly either a bug in the 1P extension, in Safari Technical Preview, or a problem in the interaction with multiple extensions together. But when doing the basic disable-extensions-until-you-find-the-problem process, it's always the 1P extension.

At first, I thought it was simply a bug in that beta version of 1P8 that wasn't playing nicely, or maybe a bug in that version of STP, but both have had updates since this issue first showed up for me in mid-February. The only one which hasn't is the 1P extension.