These are Mode S messages i.e. not extended squitter; it’s normal to get a lot of them.
c62 % had “Bad Parity PI”
This is a complicated one…
For some message types, SSR will send a query on 1030MHz that includes an interrogator identifier that identifies the particular radar.
The transponder assembles a response, computes the CRC, XORs the low bits of the CRC with the interrogator identifier, and sends the result.
The SSR then XORs its own identifier with the received message to recover the CRC. If the CRC is bad, either the response was damaged,
or it is a response to a different radar’s query - either way the radar can safely ignore it.
This scheme is “PI” - “Parity/Interrogator”
It causes a problem for passive receivers like us, though, because we only see the reply on 1090MHz and don’t see the query on 1030MHz that has the interrogator identifier.
So we don’t know whether an apparently-bad CRC means “this is an undamaged response to a SSR interrogation” or “this is a damaged response to a SSR interrogation” or “this is a damaged spontaneously-generated message”. Those messages are what VRS calls “bad parity PI”. It’s not really bad, it’s more like “it’s non-zero and I don’t know if that’s bad or not”.
So your guess is as good as mine as to whether 62% is normal or not