Recently I had some problems with one bike. It is an older bike with
the nearly horizontal forward facing "drop outs". I had disassembled
all my bikes to make it easier to load in the van when we moved to the
new house and after re-assembling the bike I found that the rear
wheel would not stay located in the rear drop outs. Riding only a
short distance would cause the wheel to twist so that the cassette
side of the axle slid forward enough that the tire rubbed on the
frame.

I had ridden the bike for several years in Bangkok - generally very
flat terrain - with no problems and the only change, I thought, was
the installation of a 12 - 34 cassette as the new house is in the
mountains.

I was about ready to try and modify the rear drop-outs to something
with a vertical opening (like newer bikes) when I got to thinking. I
had used some very sleek looking, gold anodized, skewers when I
reassembled the bike and as that and the new cassette were the only
changes I had made, just maybe...

I replaced the new, pretty, skewers with some old skewers that I had
and lo and behold the rear wheel staid centered for a two hour ride
this morning.

The pretty new gold anodized skewers that apparently weren't
clamping tightly enough to hold the wheel in place looked like
https://www.ebay.com/b/Bicycle-Skewe...825/bn_1856901
The tenth illustration down labeled "Mountain MTB Road Bike Bicycle
Wheel Hub Skewers Quick Release Bolt Lever Axle" and showing the very
pretty red, yellow, silver, blue, and black anodized skewers (THB
91.69 a set - ~US$2.88)

The old used set I replaced them with looked like the first
illustration, labeled "Campagnolo Record REAR and Chorus FRONT QR
Skewer Quick Release" although mine don't seem to have any name on
them. (THB 41.45 - a bit over a dollar)

If you are riding an old bike - a Classic is the term I use - and
having wheel problems maybe a change to the older skewers would help.
--
cheers,

John B.