Best methods for streetcars right now until bugs are fixed is have your high density streetcar avenue in a single loop with NO intersections to other Streetcar avenues, the intersections confuse them and they turn around. A loop like a horse track, the street cars go to every stop. No issues anymore.
The other method is a straight streetcar avenue, from one end of town to the other without connecting to another piece of avenue hence an intersection.
I ended up making 1 gigantic loop that turns, so my horse track looks like a indy 500 race course instead.
Streetcar avenues have to tend to your High Wealth residental, High Wealth Commercial and High wealth industry.
Also noticed putting Streetcar avenues around the outter edges of the city creates more traffic problems. Near the center around the commercial zone is the best.
I also the population drops, my city just seemed to do that, slowly increase and then decrease quite a bit but with only 3-4 buildings going vacant in a day.
Put bus stations on both sides of the road next to each trolley stop, same with Park and Go Lots. Sims are lazy and won't cross the road if a bus stop is on the other side, so place them across from each other on the same road.