multisite Allworx setup - branches crash post 8.2.x upgrade

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Working with our reseller on this issue already but wanted to see if this has come up for anyone else.

Background: we have a 16 location multisite with a 48x as the main site. Branches are mostly 6x (several with a Px 6/2 port expander) with a couple using a Connect 536. Allworx 9204 phones everywhere except one location using ACD feature, they have a mix of Allworx 9212 and 9204 phones.

Issue: after we upgraded to 8.2.x we began branch locations began intermittently having Registration Error on all phones, and the web interface would become unresponsive. Usually they remained pingable, but call functionality failed. Restarting the Allworx server generally restored functionality for a while, then issues cropped up again.

Status: our reseller talked to Allworx and while they don't know why it's happening yet they think it's related to multisite. We turned off multisite and were stable for a week. Re-added branches to multisite and were stable with 9 branches it seemed. After we get to 10 or 11 branches the issue seems to happen although maybe not as often when we were at our full 15 branches. We're rolling back down to try 9 branches to balance stability and functionality.

Question: anybody experienced anything similar either on 8.2.x or on another version? Any other feedback or thoughts? We are currently on 8.2.3.9 for reference.