Normally I would've been at the track, but my sinuses were already jacked after the dust storm hit on Friday, no way I was gonna be able to be outside for more than a couple hours at a time this weekend... I plan to be there next week for sure!
Batteries will also tend to go bad from old age too
Those bad connections can be a faulty connector on the charger too... especially if you are using "cage" style bullets, I try to use "slotted" bullets so that I can spread the bullet with a mini phillips screw driver to increase the bite. Also those 2mm bullets (for the balance port) only come with cage style connectors and they need to be replaced every year or so, I guess it depends on how often they are used.
1/8 Buggy will do fine around 5Ah, go 6.5Ah if you want some cushion, the extra weight will make it more stable anyway.
1/8 Truggy at least 6.5Ah to 8Ah if you more than enough cushion
I haven't raced TC in years, I assume you're gonna race at N-Control?
I know a 5Ah shorty will do fine for any of the stock classes, but wouldn't be surprised if folks are running 8Ah packs for mod, I would talk to Paul on this thread here just to see what most of the guys are running these days over there:
Bringing the track back on RCFiles - RCFiles Forums