Mike,
I highly recommend calibrating, yes.
The normal calibration process for most thermos is to place the probe in an ice water bath until it levels out. It should read approximately 32 degrees. Note what it reads. Then (preferably after allowing it to return to room temp) place the sensor in boiling water until it settles out. It should read approx. 212 depending on a couple variables.. I use my thermos regularly, and check mine about once every five times of use.
Using the actual readings you should be able to tell if it is reading correctly. If not, replace the probe.
I do not use that model, but similar ones and have to replace probes with some frequency. I know the TP-20 is a good one, so it should be accurate, but no guarantee without checking.
Hope this helps,
Mark