Multiple Fast presses of power button required to start PC

OK so about 2 months ago my computer started doing this before it broke. When I would push the power button, the tiny window of time that the tactile click is made, when the button was depressed halfway, the fans would light up and start to spin in the case but not boot. Apon full depression of the power button OR the release of my finger from the power button, it would return to its off state. Also, if the power button were fully depressed, (before i removed my finger and after the fans had kicked on for a hair once already on the previous push of the power button) as I remove my finger, the fans would also kick on once again on the release of the power button but again, no boot. THE ONLY WAY I could start it, was to button mash the power button in and out say oh about 3 times, so as to almost jumpstart the PC after technically 6 kicks of the fan. (one on the push of the button, and one on the way back up on the release.) if i go slow, it doesnt start/boot. only by making the window of time the fans were spinning closer together (aka pressing the power button fast) did the pc boot. So those are the main characteristics of the issue that i am confronted with NOW, once again ( 2 months later.).

Soon after this problem started, eventually my computer would no longer turn on anymore at all. I replaced the tower (Corsair Carbide series Mid Atx tower) thinking the power button was broken, nothing changed. still showed no signs of life from power button.

then I replaced the power supply (corsair RM850x) and it got me back to where i was and am now. I have to press the button fast to start. Does anybody have any idea what could cause this? i looked on here for a while but every problem i saw was not similar to mine in the sense that you have to press the power button quickly to force start it.

Thank you for your help and sorry this was so long.




Specs-
Case-Corsair Carbide series mid ATX tower BRAND NEW
CPU-amd fx-8350 with cooler master heatsink
Ram-24gb (16gb 1866 pair and 8gp 1866 pair)
HDD/SSD-1TB hdd/ 250gb samsung 840 evo ssd
GPU- 2x 7870s. 1-ASUS 7870, 2-HIS 7870 (running crossfire)
PSU-Corsair RM850x BRAND NEW
MOBO- asus m5a99fx pro r2./0