[PROBLEM] NAS unmount

[Miss Sissy Princess]

8.8.8.8 is a Google DNS server address.
Shouldn't be set on a host sat on a LAN though, would be normally used for setting a router's WAN DNS to avoid the ISP's often slower DNS services.
Either OP's manually configured this in Moode's settings or has set this in their router's DHCP settings. Either way OP's probably misunderstood what DNS is for and how an external dns server is used.

There is nothing wrong with using 8.8.8.8 (or 1.1.1.1) as the DNS server on a host unless you are relying on DNS resolution to "find" local systems by name.  If someone mounts their NAS using its static IP (or pseudo-static IP if their local DHCP server is configured to supply a fixed IP address based on the MAC address of the NAS), DNS does not come into the equation.  That the OP is able to mount the NAS at all would suggest that the problem isn't a DNS issue.

Not entirely, many services including ssh, nfs and samba will perform reverse name lookups on incoming clients whether the client is connecting to a hostname or ip, causing delays and timeouts if the name can't be resolved.

Most home and SOHO routers don't resolve DNS requests of any type; they forward them to Internet DNS servers (or fulfill them from cache).  My EdgeRouter 4 is a darned good router and its documentation states that it "includes a DNS forwarding service based on dnsmasq that is consulted when clients use the EdgeRouter as a DNS server. The dnsmasq service runs in the background and will forward all client DNS queries to the specified DNS server(s)."  

In any case, if you're seeing delays and timeouts related to DNS when using 8.8.8.8 on any local host, then something is wrong.  Try "nslookup 192.168.150 8.8.8.8" at the command line and I bet that the 'not found' response will be instantaneous (from a human standpoint).  If you substitute your router's IP as the DNS server, the result should be the same.  And I would be surprised if either returned a hostname for a reverse DNS (PTR) query for a local IP address (e.g., 192.168.x.x).