Blinker stops when brakes applied

Here is the text of what the brake light bulb says:

OSRAM 7225 LF SLOVAKIA 12V F21/4W E1 3AA T5c

It should be noted that the "E1" has a box around it, not sure if that matters or not. I don't see 1157 anywhere.

Yes, both the old and new bulbs are dual filaments. When you say pins, I'm assuming you mean on the base of the bulb that click into te socket. The old bulbs are staggered and are not straight across.

Hi, I ran a number of diagnostics with different combinations of bulbs. I've listed everything from start to finish so that you can help me isolate the issue. I am truly stumped right now.

Bulb #1: Original brake/tail light bulb - defective (smoky, off-centered pegs, originally on left tail)
Bulb #2: Original brake/tail light bulb (functions properly, straight pegs, originally on right tail)

Bulb #3: New bulb purchased (#1157, straight pegs)
Bulb #4: New bulb purchased (#1157, straight pegs)

1) Left brake light was out. Tail light on left side was working fine. Right brake and tail light was working fine.
2) Replaced bulb #1 with bulb #3. Brake light always stayed on on left side. Right side (bulb #2) was properly working. Left turn signal began blinking rapidly and left tail turn signal was not working (first time any issue with turn signal became apparent.) Right front and rear turn signal working fine.
3) Replaced bulb #2 with bulb #4. Both brake lights now were brighter than they should be, left front turn signal remained at a fast pace.
4) Replaced bulb #1 with bulb #3 and replaced bulb #4 with bulb #2. Left tail light still appear consistently bright, right tail light returned to correct brightness. Front left turn signal still blinking rapidly, rear left turn signal still unresponsive.
5) At this point, the original bulbs are in the original locations. I switched them by putting bulb #1 in the right tail and bulb #2 in the left tail. At this point, both tail lights were showing the CORRECT brightness. I tried the brake pedal and both light up to the correct higher level of brightness. However, the left turn signal in the front still blinked rapidly and the rear left turn signal still was not blinking.
6) I pushed the remote lock a few times to test it out. All of a sudden, bulb #2 (currently in the left tail light) stopped working. I switched them back so that bulb #1 is in the left socket and that bulb #2 is in the right socket.

At this point, I am completely stumped. Both before this issue and during this entire process, I turned my hazard lights on and all turn signals are blinking at the correct speed (front and rear). So, I don't think the rear left turn signal is an issue because it blinks properly when the hazard light is on. It should be noted, too, that the openings for the pegs in the socket (that the wires connect to in the tail light housings) are straight, not off-centered. I think at some point the tail light that is defective was replaced, possibly when I got an oil change, which is why it has off-centered pegs. Also, when installing a bulb into the left tail light socket, it doesn't "click-in" as cleanly as a bulb in the right socket. I am starting to think the issue is with the left tail light socket that holds the brake light (sorry, I don't know the name of the part).

Please advise! This is driving me crazy.

Thank you for your time.

I am a bit of novice when it comes to this stuff. But, I would like to learn and I don't really want to overpay for a mechanic to fix the issue, unless it absolutely requires it. Could you provide me with details on how to test what you describe above?

No I don't have either.

Hi, I ended up taking to a mechanic as I did not have the equipment to diagnose and fix myself. The issue is now fixed, it was a bad ground at the rear, thanks for your time and help.

Electrical problem
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