maverick thermometer probes

[rober]

I have a maverick ET-732 thermometer. when I checked reviews & on forums the 732 got the best reviews. I've had it over 2 years & have only had to replace the batteries once. one probe failed pretty quick & maverick replaced it quickly & without a fuss. the replacement probe was longer ( a good thing ) & seems to be of a better quality. I've only used this in my smokers. I wipe the probes with a damp cloth & clean off any build up with a piece of drywall sanding screen & never submerge them. the screen works great on build up on anything.
yesterday for the 1st time I dropped the probes thru the vent in the lid of my weber while doing an indirect grill. 10 minutes into the cook the food probe readout went to HHH. the grill probe followed suit soon after. after letting the probes cool down the grill probe worked & the food probe did not. the probes were never directly over the fire. does the temperature get really hot at the top of the lid?? just before the food probe went to HHH it briefly read 400* which does not seem possible given there was only 1 weber coal basket burning at the opposite side of the grill & the probe was inside of a 4" thick piece of pork which was not over the fire. the maverick site says that HHH or LLL it means the probe has failed or the plug is not making full contact. anyone had a similar experience?? there some aftermarket maverick compatible probes on amazon & ebay that are supped to be of a better quality. they are longer & cheaper.
this thermometer has been decent so far. the probes always read 5-10* different. knowing this going in I just adjust things accordingly. what's queer about this that when tested in boiling water or ice they read within 1-2*. it's in the grill where they read differently.
sorry for the long post.