It is the old-style method of bridging ports and VLANs which can result in layer 2 misconfiguration problems
https://wiki.mikrotik.com/wiki/Manual:L ... _interface - a quick fix is to disable spanning tree on the bridge, using a single VLAN-aware bridge for everything would be preferable.
Another possibility, depending on the RouterOS version, is the various Mikrotik discovery transmissions interfering with some VoIP devices - the workaround is to exclude the interfaces from discovery.
I hope the device isn't directly exposed to the internet given the almost complete lack of firewall rules.