Ok, having these settings like this maybe another cause.
These settings are effecting all devices connected to the router. PCs and etc. I presume that PCs and other devices do not need this configuration accept only the VoIP phones. I would recommend that you 1st, reserve IP addresses in sequence, i.e. 192.168.0.150 thru .155 for just the VoIP phones. Then, instead of using 0.0.0.0 thru 255.255.255.255 for the Local IP address range in QoS, change the LOCAL IP RANGE values to 192.168.0.150 to 192.168.0.155 for the LOCAL IP Range for each of these QoS rules. This will tell QoS that only the VoIP phones in the new IP address range to apply this rule too using the reserved IP addresses in that new sequence. All other PCs and device will not get these rules since they don't need this configuration.
2ndly, the Priority should not be 1 as this maybe another cause of the router disconnection. Priority 1 means that all bandwidth would be reserved to these devices and any other devices would be starved by bandwidth and not get much if any Internet data. This maybe why the router could be stopping. I recommend changing the priority to 50.
Then make one more rule in QoS, name it ALL OTHER DEVICEs. Input values for LOCAL IP RANGE 192.168.0.100 to 192.168.0.120. Use 0.0.0.1 to 255.255.255.254 for REMOTE IP RANGE. Select ANY from the Protocol drop down menu. Set the Priority to 128 as this value is normal bandwidth management for the devices in this local address range. Check mark the check box to enable this rule then select Save Settings and reboot now. This rule will allow any PCs or devcies connected in this range to work well with the other QoS rules and still get some priority and bandwidth and not be started for data flow. I would reserve IP addresses for the 5 PCs and any other devices, with in the Local IP Range as well, 192.168.0.100 to 192.168.0.120.