UV Mapping a sculpted object shows glitches I am going through some fundamentals in UV mapping and I am taking my first steps in UV mapping a sculpted object. The way I created the object (representing a candle) was:

taking a cylinder

apply a mirror modifier

apply 3 subdivision modifiers to obtain more dense and detailed geometry to have more details for the sculpting part

and then started sculpting.
Problem is that now I just added the plain checkers UV and I see these weird stuff happening for the first time. The candle in the Scene Collection is:



The weird stuff happening is:

Any idea of what is going wrong?
The way it should be from the tutorial I am following:
`
EDIT:
after cutting the object in half with a Seam and re-unwrapping the glitches are still there (see image below) plus you can see the weird behavior I recorded in this video:
https://youtu.be/bpuPxHHol1U
Don't apply the subdivision modifier. This makes the geometry unnecessarily dense. Re-meshing may have solved your problem but this will not hold up.
Also smart UV unwrap isn't the best way to unwrap because of lack of control. Instead make creases and then unwrap using U&gt;Unwrap&gt;Unwrap. Also learn about edge-flow. This is very important when modelling.