It is very strange to here that the F0S probe works with one gage body but not the other. I suggest performing a factory reset of gage body sn: 742248 with Probe FOS S/N. : 206328.
After the reset test the unit. If the probe still does not work, exchange the gage body. With the new body attached to the F0S probe, take several measurements ensure the probe is functioning properly. If the unit functions then the instrument should be fine to sell.
If you do not feel comfortable selling the unit, then return it to us for further testing.
If I can be of further assistance, feel free to contact me.