Stereo 45's

About a week ago, I found some good Don Williams 45s on eBay and when I received them, I noticed that most of them were in stereo. The stereo 45s play perfectly on my 8EY4 Deluxe player, but they don't play without skipping on my 45EY4 machine, and both players have the same Bosco stereo cartridge/needle. I wonder why they will play well on one player but won't play on another? These are the first stereo 45s I've found, and they are radio station promotional copies with the same song on both sides. Has anyone experienced this same problem?

Either the needle is wrong size (different model even though they look the same), or the tone arm weight

It has to be tonearm weight then. All the needles are the same.

I found out the 45EY4 has the extra counterbalance spring in the back of the tonearm, and that is likely what is causing the problem. I'm going to unhook that spring. The 45HY4 and 8EY4 Deluxe players don't have that spring.