Weird APC UPS "Batteries Discharged" alerts

We have an ancient APC Smart-UPS 5000RM. Over the past couple weeks, at almost the exact same time each night (within seconds), we get 3 "Batteries Discharged" and "Condition Cleared" alerts and we cannot figure out what is going on. Looking at the event logs, we don't see anything out of the norm. All devices plugged into the UPS are "constant power" type items: switches, cable modem, and a workstation that we use just for management in the area this is located in. There really isn't anything that would require a ton of power at the same time each night. Batteries are less than a year old install Nov of 23. We ran a calibration with no issues. Run time is good. We also have power logger on the same circuit as the UPS to see if there are any spikes or sags and haven't detected any. I'd really love to retire this thing but can't right now. Any ideas of what else I can check before buying new batteries?