Are you connecting to the router by Ethernet or WiFi? If it is WiFi, is the disconnection happening on the WiFi or on the Internet? WiFi originates in the router and does not come from the ISP. The ISP provides only the Internet connection but does not identify how that connects to your device(s).
Are you getting disconnections on more than one device or just on one particular computer? If it affects only one device, then that device could have the problem.
Do you have a separate modem? If so, connect a PC directly to the modem by Ethernet and see if you still have the problem. This will point to or eliminate the router.
The fact that your speed has dropped to 1 to 2 Mbps (not mbps, which is literally a billion times slower), suggests you are probably using WiFi.
Have you tried changing the wireless channel the router is using? Have you tried connecting to the router by Ethernet? If you have a separate modem, with the PC connected directly to the modem (by Ethernet) are you still getting the low speed? If you are, then it is probably an ISP problem.
WiFi does suffer incompatibility issues between a router and certain devices. This can appear as:
1) Failure to connect to the WiFi network, and in some cases failure to detect that the network is actually there.
2) A slow connection that may disconnect randomly and has problem passing data (such as getting DNS look-ups).
This can be affected by the actual channel the WiFi is using, and by the driver in the PC. If your computer is running Windows 10, then the driver might have been updated to one that does not suit the particular wireless adapter. I had this with a Windows 10 Ethernet adapter, which refused to work until I went back to the old driver.
Finally, you should treat resetting the router back to its factory settings as the very last resort. Resetting a router (rather than simply restarting it) can cause many problems as settings you have configured (or were configured by the ISP) can be wiped out.
I hope you find the answer, but you will have to do some more diagnosis work first.