In our old neighborhood we had 2 identical house developments.
The assessors sent 2 different people for each.
In one the house assessments (our development) came out much higher.
When I fought the tax, the town tax guy told me it was stupid, he was forced to use that assessment company and yes, they messed up and nothing they can/would do.
I won the case and my property tax went down about $600/year.
So many people won, they changed the rules that the difference in "valuations" would have to be above $150,000 dollars or the challenge would be thrown out.
If you can't win, change the rules
Our taxes in NJ were going up close to $1000/year, one of the many reasons we moved to PA, where our taxes have gone up about $500 in 6 years, even went down one year.
There are no standard rules on assessments, my Major pet peeve.