All 10.11 betas. Both 3.91 and 3.91 Legacy. Attached crash report.

Crash on launch to extract, any file. 100% repeatable.

That is odd, I have other reports from 10.11 of crashes, but they happen in very different places. This one does not seem to match. Do you have any other machines to test on?

Sure thing, I've got a laptop that had the same problem but not on me right now. I'll produce a crash report tomorrow for you.

Same here, crashes 80% with all 3 Betas until now

Further details.

This appears to be the case with multi-part archives only of a high number.

A <10 multi part, sometimes crashes but gets through with a bit of persistance. A >10 multi-part is crashing with 100% reproducability.

Here's another crash report just in case its needed.

Can you check if this works better?

No love even opening it. Generates the following three console lines.

11/08/2015 7:03:53.598 PM CoreServicesUIAgent[43177]: Error -60005 creating authorization 11/08/2015 7:03:53.607 PM CoreServicesUIAgent[43177]: Error SecAssessmentCreate: The operation couldn’t be completed. (OSStatus error -2147409652.) 11/08/2015 7:03:56.364 PM com.apple.xpc.launchd[1]: (com.apple.xpc.launchd.oneshot.0x10000018.The Unarchiver[56235]) Service exited due to signal: Killed: 9

OS X Complains it can't open and I should trash it.

Ironically this is due to a bug in The Unarchiver which is fixed in the new version.

Open it with Archive Utility for now.

Extracted the zip archive with Archive utility to the same result I'm afraid. Still asks to be trashed.

Others seem to have got it running. Could you try again, just in case something went wrong?