Thread device not reachable anymore

I am running HA OS and connected a Skyconnect with the OTBR addon. In total I have 3 border routers: HA, Homepod Mini and Google Nest Hub 2.
Then I provisioned an Eve energy plug to the OTBR which is marked as default network. That worked pretty smooth and the plug can be switched normally.
After a few hours it is not available anymore and I get the following logs in the OTBR:

Default: mDNSPlatformSendUDP got error 99 (Cannot assign requested address) sending packet to ff02::fb on interface fe80::c88:86ff:fecd:9695/veth89ea371/36
Default: mDNSPlatformSendUDP got error 99 (Cannot assign requested address) sending packet to ff02::fb on interface fe80::c88:86ff:fecd:9695/veth89ea371/36
Default: mDNSPlatformSendUDP got error 99 (Cannot assign requested address) sending packet to ff02::fb on interface fe80::c88:86ff:fecd:9695/veth89ea371/36
Default: mDNSPlatformSendUDP got error 99 (Cannot assign requested address) sending packet to ff02::fb on interface fe80::c88:86ff:fecd:9695/veth89ea371/36
Default: mDNSPlatformSendUDP got error 99 (Cannot assign requested address) sending packet to ff02::fb on interface fe80::c88:86ff:fecd:9695/veth89ea371/36
Default: mDNSPlatformSendUDP got error 99 (Cannot assign requested address) sending packet to ff02::fb on interface fe80::c88:86ff:fecd:9695/veth89ea371/36
Default: mDNSPlatformSendUDP got error 99 (Cannot assign requested address) sending packet to ff02::fb on interface fe80::f015:4dff:fe54:e744/veth1866c52/38
Default: mDNSPlatformSendUDP got error 99 (Cannot assign requested address) sending packet to ff02::fb on interface fe80::c88:86ff:fecd:9695/veth89ea371/36
Default: mDNSPlatformSendUDP got error 99 (Cannot assign requested address) sending packet to ff02::fb on interface fe80::f015:4dff:fe54:e744/veth1866c52/38
Default: mDNSPlatformSendUDP got error 99 (Cannot assign requested address) sending packet to ff02::fb on interface fe80::c88:86ff:fecd:9695/veth89ea371/36
Default: mDNSPlatformSendUDP got error 99 (Cannot assign requested address) sending packet to ff02::fb on interface fe80::f015:4dff:fe54:e744/veth1866c52/38
Default: mDNSPlatformSendUDP got error 99 (Cannot assign requested address) sending packet to ff02::fb on interface fe80::f015:4dff:fe54:e744/veth1866c52/38
otbr-agent[183]: 3d.10:14:36.183 [W] Platform------: failed to send ICMPv6 message: Cannot assign requested address
otbr-agent[183]: 3d.10:14:36.184 [W] RoutingManager: Failed to send RA on infra netif 2: Failed
Default: mDNSPlatformSendUDP got error 99 (Cannot assign requested address) sending packet to ff02::fb on interface 192.168.178.156/enp6s18/2
otbr-agent[183]: 3d.10:14:36.227 [W] Platform------: [netif] Failed to process request#15: Operation not supported
otbr-agent[183]: 3d.10:14:36.227 [W] Platform------: [netif] Failed to process request#16: Operation not supported
Default: mDNSPlatformSendUDP got error 99 (Cannot assign requested address) sending packet to ff02::fb on interface fe80::f015:4dff:fe54:e744/veth1866c52/38
Default: mDNSPlatformSendUDP got error 99 (Cannot assign requested address) sending packet to ff02::fb on interface 192.168.178.156/enp6s18/2
Default: mDNSPlatformSendUDP got error 99 (Cannot assign requested address) sending packet to ff02::fb on interface fe80::f015:4dff:fe54:e744/veth1866c52/38
Default: mDNSPlatformSendUDP got error 99 (Cannot assign requested address) sending packet to ff02::fb on interface fe80::f015:4dff:fe54:e744/veth1866c52/38
otbr-agent[183]: 3d.10:14:36.618 [W] Platform------: failed to send ICMPv6 message: Cannot assign requested address
otbr-agent[183]: 3d.10:14:36.618 [C] RoutingManager: RsSender: Failed to send RS 1/3: Failed
Default: mDNSPlatformSendUDP got error 99 (Cannot assign requested address) sending packet to ff02::fb on interface fe80::f015:4dff:fe54:e744/veth1866c52/38
Default: mDNSPlatformSendUDP got error 99 (Cannot assign requested address) sending packet to ff02::fb on interface fe80::f015:4dff:fe54:e744/veth1866c52/38
Default: mDNSPlatformSendUDP got error 99 (Cannot assign requested address) sending packet to ff02::fb on interface 192.168.178.156/enp6s18/2
Default: mDNSPlatformSendUDP got error 99 (Cannot assign requested address) sending packet to ff02::fb on interface fe80::f015:4dff:fe54:e744/veth1866c52/38
Default: mDNSPlatformSendUDP got error 99 (Cannot assign requested address) sending packet to ff02::fb on interface 192.168.178.156/enp6s18/2
Default: mDNSPlatformSendUDP got error 99 (Cannot assign requested address) sending packet to ff02::fb on interface fe80::f015:4dff:fe54:e744/veth1866c52/38
Default: mDNSPlatformSendUDP got error 99 (Cannot assign requested address) sending packet to ff02::fb on interface 192.168.178.156/enp6s18/2
otbr-agent[183]: 3d.10:14:40.286 [W] Platform------: [netif] Failed to process request#17: File exists
otbr-agent[183]: 3d.10:14:50.282 [W] Platform------: [netif] Failed to process request#18: File exists

That looks like a network issue but any idea how to solve this?

As an additional observation: the device comes back again after a few hours. This procedure happens roughly once per day.