3.5 is the maximum load for Red Dot for 38 Special. 3.8 grains is +P. I use red dot and your exact bullet and load 3.2 grains. Don't have a chronograph but the 3.2 is right in the middle of the road for that recipe.

Dumb question since I'm new at reloading, but have you checked your scale with check weights? I do that before every reloading session. I weigh every charge and red dot fluctuates pretty wildly for me. I have the thrower set for 3.2 grains and 8 times out of 10 I have to use the trickler to get it up to the 3.2. When the powder is gone (and it almost is) I'm not gonna use it anymore. Just doesn't meter that well.

New as I am, I guess my opinion doesn't matter much, but squibs mean not enough power to leave the barrel. So it's either too light a charge (or none at all) or the case tension is so loose that the pressure isn't enough to really launch the bullet. And I gotta think that there would be evidence of that in the case and well as in the cylinder. Do you check every case before you seat the bullet? Do you load on a progressive press and maybe those 8 rounds didn't get any powder at all?