Napier.Nomad

2007 Audi Q7 V6:
I replaced the brake light switch 2 weeks ago. Brake lights work fine, but a couple of days later I have an EPC warning light on the dash and the engine is not responding as it should. Then the car occasionally will not let the key out of the ignition after I park and turn off the ignition.
I broke down and purchased the VCDS connector and software this week (thank you Ross-Tech for the speedy delivery).
I take a read with the auto-scan and its telling me:
Fault found:
001393 - Brake Switch (F)
P0571 - 008 - Implausible signal

This shows up in the engine and transmission section.
In the Acc/Start Auth. section:
Fault Found:
00230 - Transmission Park Selector Switch (F305)
010 - Open or Short to Plus - Intermittent

I also have a scattering of Supply voltage and under voltage errors, but I'm sure they are due to the brake lights staying on all night and running the battery down.

I clear all the codes, and everything runs great. I drive a couple of miles down the road and after multiple applications of the brake, the EPC light comes on (I know what the problem is this time). At the end of the day, after getting in and out of the car multiple times with no issues with the ignition key, the ignition key will not come out. Luckily it waited until I was parked in my garage for this to happen.
I take a read on the error codes this morning and same 2 DTC's, brake implausible and park selector.
Obviously there is an intermittent problem with the brake lights and possibly one with the park selector micro switches. I haven’t had a chance to get under the dash and check all the connections for the brake light switch.
Has anyone had an issue with a brand new switch giving an intermittent issue like this?
Also, could the error with the switch cause the ECU to freak out enough to think the park selector switches are faulty or due I need to assume these are faulty and go ahead and plan on replacing them?
Your inputs would be greatly appreciated.