I Bought T100 2015 Only 1000 Klm, Whit A Little Snag!

What are the weak points 05-16 T100 Voltage, Battery

My recurrent problem is, once in a while hot or cold , batterie charged; i press start button, got quick reaction then cut (just to engage starter) may repeat 2 to 4 time before i get a good turn over.
I did A) Opened the push button & I polish the little pin & spring. Before closing cleaned whit contact cleaner. seem ok for a while, then will reoccurred. Also tough the neutral switch B) while holding start button when it does it (cut ) i play whit the clutch lever, (no change) nothing will happen!
Tried turn to turn off ignition, (computer related ? ha ha) But will always end up by cranking over at one point
Just when out and did it again, so checked again: Cleaned batterie & tight post, same starter relay post.
Can a 6 year old battery, be weak or not keeping charges?

 

"Quote " (system computer not letting it start because it’s dropped in voltage output by very little more than likely)
"I took that in consideration"
So i started de-snag right from beginning,
I have a very old trickle charger, (seemed to take for ever to charge )
So replaced for new smart one, After a couple hrs (even if sill showing charging)
Already saw a difference, starting every time and sounded stronger cranking too.
So it might of looked to deep to solve the problem.
Result 1) A good trickle charger, 2) And replace my 6 year old battery that don't know the history Bike stored in Ontario none heated shed.
Thanks,