Scheduled Emails Failing - Causing Exception when Processing

Have any other NetCommunity clients been having issues with scheduled emails failing? We've had this happen more than four times over the last few weeks - where it's only happened once or twice in the entire year previous. (We've recently migrated from self-hosting RE to RENXT.) The Email Status report shows an exception, and when this happens we copy the email and resend (deleting the one that has failed). When resent, it has delivered without fail each time - and we're not changing the queries!


We've read through this article, https://kb.blackbaud.com/articles/Article/69258, which shares about this error and recommends that the queries are too complex. But, they are as basic as we can possibly get them to meet our communications strategy (examples below). I would appreciate any advice on how to combat this - thanks!