I see. Then try to clean the grease on the part that goes into the reel, eventually roughen it with sandpaper so that the friction only occurs on the other side. From the above pictures, the 2 springs looks about the same length. I assume the force of the spring when you compress them is about the same on both.
It seems I was finally able to fix it. Upon further inspection I noticed, that part of the friction between the reel and wheels is created by a sort of tight fit between the reel and the lower wheel axis. So I put a thin layer of silicone grease on the lower wheel axis to increase the torque - marked red on the picture. New reverse play take up force is 70. Now reverse and auto stop works perfectly in both directions. Sadly this fix worked just for some time, so I cleaned the grease thoroughly and added one layer of thin duct tape and put some grease on the duct tape. So far it seems to work reliably ...
I'm really glad to hear you were able to finally fix it ! This tight fit creating friction makes a lot more sense than the spring. I remember of a very thick grease used in cassette door opening mechanisms, to make them open slowly. If you need to do it again, this might do the job. Unfortunately I don't know the name of that grease, I would like to buy some myself.
The thick grease IMHO is the mentioned silicone grease. It's also used to grease coffee machines. I originally bought it as a thermal compound, tested it on cassette door opening mechanisms and it works well. I use better stuff as thermal compounds now - the white or silver stuff. Samples: https://www.ame.cz/Elektronika/Dily.../Silikonovy-tuk-26350005-WEICON-5g-d108258674 https://www.ame.cz/Elektronika/Meri...aradi/Chemie/Silikonova-pasta-5-gramu-d177883
