Some times, after a bit of wear occurs, the parts show interferences from mis-alignment of the tube vs. the feed throat (flat piece on the tube top rear, barrel chamber positions directly over this) and sometimes the edges of the frame. If, for instance, the hole is slightly to one side more than the other, or if the tube is mis-positioned in some other similar manner, the edge of the tube may have more interference where it meets the frame seating area. (See feed throat in image, description near bottom of post)
The edge is always cut with a small taper or chamfer at the factory to make the follower have a proper seating area, and normally the fit is OK. After all, the follower is spring loaded to "pop" against the shoulder after the last shell clears. If there was a consistently poor fit in this situation, the follower would get a "wedging" action in very short order. Sticking followers would be the order of the day.
There are some special metal and plastic "anti-jam" followers available, but these are to help normal guns become more reliable under adverse conditions. The old-style factory metal follower is an upgrade, also.
The mis-aligned condition can cause the factory tool (also cleaning out excess silver solder bits at the same time) to fail to cut perfectly all the way around, or may not be cut to a sufficient depth to eliminate the "catching or wedging" condition.
The picture attached has a few points of interest. The edge of the feed throat is visible, from the underside perspective, as well as the long springy feed latch adjacent. Look at the magazine tube interior, just behind the feed throat, and you will see a patch of roughness. This mark is from the silver-soldering process to affix the feed throat into position. Sometimes that is a very rough mark, and I have seen little slivers of metal start to peel.
This area is able to be carefully smoothed, but the metal is very thin at this area, sometimes, and smoothing from grinding could cut through into the silver solder, so be careful. Sometimes less is more (prudent).
See my posts on THR, also.