You said they're not in production. Does that mean there are existing APs still online alongside these new ones? If so, the situation may improve after the old ones are gone.
Either way, when swapping/installing new APs, it's best practice to do an RRM restart. This results in the controller making aggressive channel and Tx power changes, so it could be disruptive and best done during off hours.
9800:
ap dot11 24ghz rrm dca restart
ap dot11 5ghz rrm dca restart
ap dot11 6ghz rrm dca restart
8540:
config 802.11a channel global restart
config 802.11b channel global restart
I also have found 2.4 coverage issues due to too many 2.4 GHz radios going to monitor mode, and/or the 2.4 radios power up higher than the 5 GHz radios (typically you want it the other way around). There a few a few ways around this. You may need to improve the design (i.e. make sure AP locations are zigzagged and that there aren't too many of them too close together unnecessarily), you could change TPC in your RF profile to lower the maximum dBm the 2.4 GHz radio can broadcast on (which should theoretically allow more radios to stay client serving, but I haven't tried yet), manually set certain AP's 2.4 GHz radios to client serving and leave the rest on auto, or disable 2.4/5 GHz FRA entirely and monitor your 2.4 GHz channel utilization to make sure it's not too high due to channel overlap.
Yes, surveying is the best way to determine coverage, but you could also check each AP's Rx neighbors to see the RSSI that each AP sees the other at to help give you an idea how the signal is propagating from one AP to another.
