During workout watch 8 is skipping bpm. Is that correct

No it should detect it throughout workouts that are meant to measure it. Unless you turned on the Reduce GPS and heart rate readings feature below.

The main causes of unreliable readings are

1. Strap too loose
2. strap far too tight,
3. Ink tattoos in the wrist.

For the reduced readings setting see

Use Low Power Mode on your Apple Watch - Apple Support

in section

"Preserve more battery life with reduced GPS and heart rate readings"

"Snug" is a subjective thing, but means contact is maintained with the LED panel at all times , that is you cannot cause an air gap by moving the wrist, but not so tight as to cause pain after some hours or wearing.

My definition is you can get the end of your pinkie between inner wrist and strap but not a forefinger.

Gapping is likely to create an artificial spike in BPM in all sport watches I have used before.

Go back to Apple support and have it looked at

Genius Bar Reservation and Apple Support Options - Apple

and/or

Apple Support