Can a blind that hangs down on one side be fixed?

At the bottom of the blind, you will find two small plugs. They cover the string for the blind. Take this plug out and you can adjust the string so the blind is even. Warning: this is an over simplification.

I did it once by untying the knot at the end of the string and pulling on one or the other to find the one that pulls up the side that hangs down further. I pulled that string until they were even, then reknotted the pull string so they were even.

Possibly if you can figure out what the cause is. If it just a string issue you can repair that yourself it is on line and I believe on this site. If it is not level from the top it may appear to be hanging more towards one side when it's justa matter of rehanging them, if you see them bowing then you know that it is just time to replace it. Good luck first observe them and thoroughly check them out to figure out what cause is and then you can address the problem.

Have you tried manipulating the strings? My first step would be to try to try to make the strings even. If they are, in fact, uneven, you can remove that bottom piece that anchors the strings and work from the bottom. I've done this, but it's been a long time. It wasn't a fast fix, either, but it worked.

Regular blinds are so cheap, I would be tempted to replace rather than deal with the cords.

At the top of the blind where the up/down cords go there are a couple of small (usually brass) rollers which are supposed to grip the cords when you release them. You will probably find that one of the cords is not being gripped and therefor is allowing one side to hang down. Try pushing the rollers onto the cords with a small screwdriver

I've always been able to fix them by pulling on the strings to figure out which string controls the drooping side. Raise the blind up half way, then pull on the string which controls the drooping side till its even and level. Raise and lower to see if it works.

Here's another hack if it won't stay up .... https://www.youtube.com/watch?v=L8JxdQKyhGY