The Tokarev pistol, and most clones save the Yugoslavian M57 with its longer grip, has a magazine designed to hold 8 cartridges of 7,62x25mm ammunition. If you loaded 9 or 10, it has definitely been modified.
You can see the follower has a ‘tail’ at the back, which I measure just under 23,5mm. This limits how far you can push the follower down, normally to just a hair over the 8 round capacity. Load any more, and there's no way the tail is original.
The mag. body itself is just over 10 cartridges tall, but the compressed spring below it will take up some room; I doubt even a tail-less follower would allow 10 shots, without also altering the spring.
A source (the
Tokarev Do Everything Manual) gives a relaxed length for the mag. spring as between 6-1/4" to 6-3/4". If it is outside this range it is worn or intentionally stretched or cut, and should be replaced. (Count the loops on the picture, there's 15,5 of them plus the short one under the follower*.)
If the spring was cut (weaker), and the follower modified so it might tilt while feeding, it will certainly lead to problems just like you describe: soft feeding as you take more rounds from the mag.
How many magazines are we talking about, just two matched to your pistol? It would be odd, but maybe the previous owner performed this modification to personalize his gun. With an un-issued Polish model that's less likely. I
have received mag.s still packed in grease, where the spring or the bottom plate were in upside-down, so someone at the arsenal doesn't necessarily know what they're doing.
It
may be possible,
carefully, to grind the tail of the follower enough to allow a ninth round in the magazine to still feed reliably with some testing. Loading that last round will be tough, though, as the spring must be pressed down to its absolute limit. It's more trouble than it's worth, to me.
*This may be different depending on the country of manufacture.