Skype for Buisness Disconnects

Recently (perhaps after an upgrade to 5.6.7 - I can't directly correlate this) we've begun having connectivity issues with our SD-WAN balancing.

One of the most consistently repeatable issues is that Skype for Business will randomly disconnect completely and, more often, message sending/receiving will simply fail.

I have a ticket open with Microsoft already but I'm looking for ways to prove/disprove the firewall as a culprit in the mix (MS has already asked if it happens outside the office - we don't use it outside the office very often but I've not observed issues on my home Internet connection).

Any suggestions?

*This may be the wrong forum - moderators feel free to move to more appropriate location.

Thanks,

Ryan