Tracer rounds for all weapons have become completely invisible during the daytime. This includes all small arms and HMGs, as well as APC and tank cannons. This is gamebreaking for the many vehicles and weapons that rely on tracers. The only weapon that still has visible tracers is the RPG projectile.
Tracers appear absolutely normal at night or in low light conditions. One player reported that tracers reappear at 18:45, but this likely depends on map and date.
2 other users from the forums have confirmed this bug so far.