Eratic Temp Readings

I was having Illegal Operation Errors on WD, after running great since I started running it for several months, so I upgraded to 10.12q and now I am having Temperature readings that are 6-10 Degrees High. I have not noticed any other readings being off.
Does anyone have any ideas on where to look for the problem? I have tried different “Data Length” and other settings, but no luck.
I will say the readings are correct for a minute or two, then the temp jumps the 6-10 degrees. Sometimes it varies 2-3 degrees in a 1-2 minute time frame before making the big jump. Restart the program, and it happens all over again.

I am running Window 98,and have a Peet Ultimeter 500.

I also have never been able to get the rain guage to work, but the Temp problem is my priority.

Any help would be greatly appreciated!
Thanks!
Andy