After recently upgrading a few Audiences to RouterOS 7.1.1 started noticing a few bugs on what was a rock solid device till now.
With the device being upgraded some clients inexplicably loose connection and is not able to obtain a DHCP IP address. This happens only for a few clients (HP Printers is one example) where the device successfully connect to the AP and can be seen as associated. But the device does not receive an IP address.
Doing packet captures on the Wirelss interface it can be seen that the DHCP packets are being sent, but at the same time these packets are not visible in the LAN interface. It seems these packets seems to get lost during bridging. This happens both in the Wirelss 2.4 and 5 GHz ranges.
Downgrading the device to the lower version of RouterOS immediately solves the issue and so it seem that this is an issue with the 7.1 release. To test this the AP was upgraded multiple times and every time the issue is reproducable on the 7.1.1 code