One of our company trucks has a Retrax [unsure of model, no labels other than the Retrax badge] cover on it.

When closed, it's even & proper with the tailgate.

After a bit of jostling, the passenger [non-latch] side is askew, enough to have a gap & allow water into the bed [significantly more than if it stayed fully closed]

Do not have the manual, and am not sure if there is supposed to be some sort of latch on the passenger side [or maybe some kind of friction hold].

Anyone knowledgeable on these, and have any troubleshooting tips? Can try to grab a photo next time I get out o our warehouse, where the truck is parked.

You might try here to find the model https://retrax.us.com/ .That will probably help finding an answer for your issue

Looking at the comparison, it's either a Pro XR, One MX or One XR, as it's separate key locked.

I don't think it's a Pro XR or One XR, as it doesn't look like it has the rack compatibility.

So, based on their site, I'm guessing a One MX

Looks like postimg is still not playing nice, so I can't post the photo of the gap at the moment.

Edit: Let's see if it works
I can pull it to the end, but after driving a bit, it retracts to this position.

Know nothing of the brand or how its installed but the first thing that pops out to me is the bed square.
I would try to completely olen it up and measure from corner to corner in an X patter to see if the bed is square to start with.

https://realtruck.com/p/retraxone-mx-tonneau-cover/ .Here is an install video. Looks like there is only one latch. I would check to make sure neither side rail has moved.

Have a retrax. Here is how I fixed mine. I called retrax. I gave them the details including the serial number. I asked for replacement parts. They sent them at no charge.

I pulled the system out. I installed the new box side plate that has the spiral alignment feature. I reinstalled the box top. No issues.

Call the man.

I finally got sick of mine, and tossed it in the garbage.

The day I bought a diamondbackHD was the best day for my pickup.

Zero Ragrets.

Don't look back...just do it.

It's a company truck that I was driving for a week or so, giving a small consideration to buying it.