Confusion about FRER

Why would I get a faint, but clear, positive on a dollar store hpt but barely any second line on a FRER?

I have taken 3 dollar store HPTs the past two days and they are positive. I have also taken 2 FRER (one with FMU) and they could easily pass as negative because it took about 5-6 minutes for barely barely anything to show - and of course at the 10 min mark, and when they are dry, you can see a faint pink line (and also when held up into the light)

I’m so confused. Has this happened to anyone? I’m 2 days passed expected AF and with my first pregnancy I got blazing positives 3 days before AF on a FRER.

Can anyone shed some light??