I've two dishes on the roof of my apartment building pointing to 61.5 and 119 W respectively. The signal strength to 61.5 is 99% but 119 W is just 43%. I got professionally installed and the guy who installed was amazed why 119 W signals are so low despite he got maximun strenght on his meter. Is it a switch problem?
It's likely somewhere between the dish lnb and your receiver.
Try the lnb connection and the diseqc switch. You are probably right that it's the switch acting up. They are so cheap, I would just buy another one and install it to see if anything changes...
I'm assuming your technician did some troubleshooting and checked for sky obstructions, cable connections, switch-lnb settings in the receiver, and your switch.
This may be a long shot, but, your lnb for 119, is it linear or circular? For 61.5 you need a circular lnb. (e.g. if you've tried to move an lnb from 121, which is linear, you will get a crappy signal).