Trackpad sometimes doesnt work

Is there any chance that it may happen because of keyboard? In this model Trackpad and keyboard are different unit and connected to motherboard with separate flex.

No/very unlikely. Keyboard dataline is routed directly to trackpad which controls both devices and them returns them to T2 as one device. Did you inspect the cable and its connection on trackpad side?

I have changed the flex and found that flex is fine. i used my old flex with a good trackpad and everything works fine, so my trackpad flex was fine. Everything works fine only when i replace the trackpad. during these process trackpad flex got damaged and now keyboard also not working. If i use good trackpad flex with my old trackpad (broken) then keyboard only works, trackpad doesnt work as before. That means there is some connection between trackpad and keyboard. there should be some dataline between trackpad and keybaord although they are different unit and connected separately to motherboard.

A swollen battery may push against the track pad and be a possible cause in case that hasn't been noticed.

@reyazulzannat keyboard decoder is connected to trackpad, dataline is bridged through logicboard. as i mentioned, trackpad has stm32 controller which acts as both keyboard and trackpad devices. you need known good parts to troubleshoot. you can use A1707 trackpad / cable to diagnose, howewer cable is slightly different and wont fit.