Thanks for posting! Your channel balance appears to be an older version of the S370-23. Since your balance is stamped with a 23A, I suggest selecting the 2210 stamp. Although, you may want to double check that your sash does weigh between 5 to 8lbs.
The top sash guide appears to be similar to the 18-065. Look over the dimensions and compare them to your existing guide to determine if this will be a fit for you.
It is my pleasure to assist! I'm glad that we can provide you with the parts and information you need.
In regard to the stamp, I do understand that yours is stamped with a 22A, my apologies for the typo. However, the recommended stamp would still be the 2210. If you are uncertain that this is the correct stamp, the next best thing to do would be to weigh the window.
Hello, Renzo. I'm sorry to hear you're running into this issue. There could be quite a few different explanations for why this is happening, but the biggest culprit I can think of is the top sash guide. I would check to make sure that the balance on that side is properly settled under the guide. Maybe remove both the sash and the balance and then see how they interact off the window; sliding the balance up to the top sash guide by hand might give you an idea if there are any obstructions that are preventing it from being seated. Also make sure to check the track itself for anything that might get in the way.