It does not make sense that it is HA.
It could be your hypervisor or your router/AP.
If the hypervisor and router/AP have overlap in the subnet, then it can happen or if the AP is segmenting the WiFi networks.
- How many devices do you have on the 2.4Ghz band?
- Are these all HA related devices?
If not: check if a non-HA related devices go offline as well. - Check the logs from your AP, specifically for the 2.4Ghz band.
As @WallyR wrote: it doesn’t make sense that HA is cause for this.
HA is connected by ethernet to your LAN and communicates via your AP to the wireless devices.