Pheonix miner Invalid Shares

I am getting error Pheonix miner Invalid Shares with the following miner switch:

-openclLocalWork 64

I have a modified bios for 5700XT. Without the switch, I am getting around 55MH/s without any errors. With the switch, I am getting around 59MH/s, but with errors.

Can I reduce or eliminate these errors by changing any of the OC settings?

Any setting other than 32 in this variable will result in errors.
Drop the variable altogether or set to 32.

Is there any advantage of using 32 vs. no variable?

No difference as the default value is 32 when not explicitly expressed.