Hi gravityguy and welcome
You can test if it is a problem with the ARC Pro powerbase by placing the powerbase in a small oval of track. See if the power issue re-emerges. If it does, turn the powerbase 180-degrees and see if the problem stays on the lane or swaps with the powerbase.
If the issue keeps moving with the powerbase, then it’s a problem with the powerbase - either the track joins (see fixes below) or the electronic unit itself (you’ll need a new one). If the problem stays on the track, then it’s a problem with the track. I presume you’ve tried different cars and controllers to eliminate a fault with one of those.
In my experience, almost all power problems (including lane changer power) can by solved by careful track building and maintenance - particular care being taken of the connections.
So no gaps, only nice straight joins - no forcing that final connection at an angle. Track should be kept clean (and conditioned with INOX - see
here). Probably the most important maintenance step to avoid conductivity issues such as yours is tightening the tabs underneath the metal track connectors...
If a tab is very loose, the cars will stop on that track piece every time. Lots of ‘quite loose’ tabs will have a cumulative effect and the exact problem might not be so clear-cut. I check tabs every time I build a track and tighten them if necessary.
At 85 feet, your track probably needs a ‘power tap’, ‘booster’ or ‘jumper’ to distribute the power to the furthest parts of your layout. Even when the track tabs are nice and tight, every connection will create a small power drop. By the time you get to 40 feet away from the powerbase, that’s 40+ connections and 40+ small power drops. I wonder if your power issues are worse the further away from the powerbase you get? Is this where the glitchy lane changers are?
Power taps are simply wires that attach one metal rail near the powerbase straight to
exactly the same rail on a track piece further round the track. One tap would go to halfway round the circuit. Two power taps would go to one-third and two-thirds distance.
Scalextric used to make ready-to-fit power tap cables. Some retailers now make and market their own versions (see
here). Or you can make your own with the correct components and tools - including basic soldering skills.
So... Check powerbase in an oval to diagnose the problem. If the issue is the track, clean and condition the rails, check metal and plastic connections, tighten rail tabs under the track and consider a power tap or two.
I hope that helps and gets things working nicely