Flighty Milwaukee TDS Meter

[Musing.Dog]

I was given a Milwaukee CD97 TDS meter by a friend. The meter is more than a few years old. I am new to using TDS meters but I don't think its behavior is normal.
When I test a water sample the meter never stabilizes. It continues flashing seemingly random numbers the whole time it is on. It will show the "temperature equalizing" icon a couple times in the beginning, but after that it's just random numbers.
These numbers are between 85 and 600 generally. The changes are usually larger than 50 units but frequently 100+. I have no idea how to read a display that jumps from 200 to 500 and back to 180 then to 333.
The booklet in the case says to replace the batteries when the display fades or the unit won't turn on. I have neither of these issues.
I did a Google search for this and found someone with a unit doing the same thing. They just purchased a new meter. With the low price of TDS meters, is it a good choice to buy a new one?