There were reputed to be significant changes in the 128 version regarding hanging. Perhaps try it as it was released some time ago now.

Thanks for the response...

I'm using TB 115.14.0 (32-bit), and only get offered updates for this version.

I assume the 128 version is 64-bit TB. Can I upgrade to the 64-bit version without losing my in/out boxes, address books etc? I don't want to lose anything or create worse problems.

Things do go missing occasionally in the conversion from 32 to 64 bit, however you can force a resumption of the original profile if Thunderbird tries to create a new one. using the -allow-downgrade command line discussed here https://support.mozilla.org/en-US/kb/dedicated-profile-thunderbird-installation#w_can-i-change-which-thunderbird-installation-uses-my-previously-shared-profile

Thanks again.

Not sure I want to take the risk of installing the 64-bit version, even if downgrading back to 32-bit would be possible. So I'll just put up with the download delays, at least for a while.

If I decide to give the 64-bit version a try, I'll be sure to image my drives first for easy/quick reversion, if things get out of hand...

The dataloss issue cited by Matt is https://bugzilla.mozilla.org/show_bug.cgi?id=1911076

It was fixed in 128.1.1, only affects folders that are bigger than 4gb, and only affected 32bit Thunderbird (not 64bit). So it does not affect users moving from a 32bit install to a 64bit install.