Atrostart 2106 has bad range

TL;DR - Astrostart 2106 has poor range. Checked everything I can check. Symptoms are random and location based. Remote seems to be working fine. Dealer wants outrageous amount for 10yo new remote. Looking for options.

2002 Chevy Tahoe
Astrostart 2106 5-button No alarm

I purchased the vehicle with RS already installed. Ever since I bought the vehicle I've always thought the RS has had poor range. The car I had before the Tahoe had the 2205 installed and that RS was amazing!

Correct me if I'm wrong but wasn't the 2106 rated for like 1000ft or 2000ft? Sometimes I can stand right next to my truck and not have it functioning at all but after 8 tries of unlocking doors, then all the sudden it works. Specifically there's a spot (Target parking lot) in a neighboring city where it just won't work at all, period. And by my work it randomly works just fine or not at all.

I'll start by saying that this isn't a button issue on the remote. I've taken apart and cleaned contact multiple times. The remote seems to be functioning just fine. And what I mean by that is the light blinks every time I'm using it. But I don't know if there's something else going on in the remote that I can't visibly see. I've also had the same symptoms right after replacing the batteries.

So far I've checked the following: Checked antenna connectors at windshield and brain box, checked antenna wire from window to brain box, antenna wire is away from all other wires. I've cleaned the antenna contacts on windshield. Everything checks out as OK in my book. No loose wires at connectors, no pinching or cuts.

I've attempted to reprogram the remote by using the dip switch 8 method. Seemed to take but not sure if it really re-programmed it or not. Same symptoms after doing that either way.

I'm at wits end with this thing!

Theories:
- Something in the remote is wore out. The antenna, a little relay, a capacitor, a "something something". The light still works fine but after that, something isn't functioning the way it should.
- The antenna is somehow messed up. This has the antenna that has the pinstripe sticker stuck the windshield and then you velcro the plastic part to that with those chincy foam connectors.
- There's a bug happening in the brain box. Is there a way to reset to defaults or something?
- This "older" style of RS is using some radio channel that is now flooded with other random signals like cell phones, wifi, power. Something that is causing major interference.

Does anyone know what is going on?

I don't want to just start buying new antennas and remotes just to try it out. Especially because there's a dealer by me that is still wanting $60!! for a new 5-button remote. Ridiculous if you ask me for a RS that's like 10 years old. I've searched online and can only find used remotes, which I wouldn't have any confidence in.

Is it the remote, the brain, antenna? Any ideas? I feel like it could be something really simple.

Thanks for any time related to this. Of course I'm in a situation where I can't just install a new RS or frankly spend any money on this. The wife doesn't see this as a priority by any means. Really just looking to see what my DIY options are or if I ultimately just need to save up for a new one somehow.

I was kind of wondering if it would somehow be possible to program a different brand or type of remote to this brain box. I would imagine there are limited channels that these remotes are working on, right? I mean, could I program a newer RS-613 or RS-614XR to this brain box?

Sry long post.