On Failover DNS Resolver not working

[maxx8888]

When my LTE Line fails and pfSense is doing a failover to my ADSL Backup Line, DNS Resolver cannot resolve any Address.

I'm trying to resolve e.g. google.com from my PC, during LTE Line is down, but it fails.
When I'm trying to resolve same Address on pfsense Webinterface, it takes ages but it succeeds.

I've 4 Nameservers setup. LTE Line have 2 assigned (8.8.8.8, 8.8.4.4). The ADSL Line have 2 Provider specific DNS Setup.

pfSense Default Gateway is set to LTE Line.
Tried to restart ubound Service during Failover, no change.

Do i need to set Default Gateway switching to on, or something similar?

The Webinterface DNS Result when both Lines are up:
127.0.0.1 73 msec
195.3.96.67 47 msec
213.33.98.136 23 msec
8.8.4.4 41 msec
8.8.8.8 51 msec

The Webinterface DNS Result when LTE is down:
127.0.0.1          not found
195.3.96.67      47 msec
213.33.98.136 23 msec
8.8.4.4              not found
8.8.8.8              not found

[Soyokaze]

Didn't you specified 8.8.8.8 or 8.8.4.4 as Monitoring IPs in routing section for your LTE provider?
If not, what gateway is selected for these addresses on General Setup page?

[cmb]

You need to enable forwarding mode in Resolver, or default gateway switching.