Strange discharge behavior with my 18650's

So I had just finished upgrading my battery pack from lipo pouch battery to a 12s4p 18650 pack I had made using Samsung 25R’s (green ones), and a BMS from The cells should be authentic as I have purchased them through what I believe to be a reliable distributor, I took my board out for a spin the other day, the LED monitor showed a 54% charge initially, however as soon as I started going the percentage quickly began dropping, at around 1% every couple seconds. if I then released the throttle or just stopped it began increasing again at the same rate till it was back to the initial percentage. I have never experienced this when I had the lipo pack b4 and am a little concerned. Has anyone else seen this or can offer an explanation?

That is the voltage sag causing due to very low discharge rate of batteries, may be the are on 50% but , the batteries you have might not be genuine.

The correct reason is the discharge rate of your batteries is too low that , due to increase in amps discharge of batteries, the volatge falls

Interesting, thanks for the tip. Also I just realize I misspoke in that it is a 12s3p pack not 4p. The 4p pack was another one I was building for an ebike currently.