and 18Fs are actually a bit much noise sensitive than 16Fs.

10K to 1.5k seems a big jump, but if this working...

100K - 1M internal Pull-up, are better than this. Not something i would use/trust myself in a noisy environment 100000 X

Now, maybe i'm wrong, i didn't read the whole thing once again, but it might be caused by a Read-Write-Modify thingy.

General 18Fs rules, You write to PORTx, you read from LATx.