Yesterday I was playing Tinker as the Dire in a US-East/West matchmade game and his Heat-Seeking Missile spell was visible early game but at some point after level 6 the missiles were invisible but still applying damage from my perspective, I could also hear the sound of the missile. I'm unsure if my teammates or enemies could see the missiles or not, although nobody said anything in chat so I assume they could not see the missiles. Unfortunately I didn't get any screenshots or video but I could try to replicate it if needed. Hopefully this bug wasn't already reported since I couldn't find it in the search and decided to make a thread about it.

Not sure if these will help but might as well add them: Everything in the settings is either turned to On or High except for Color Blind mode. Played in 1920x1080 with borderless windowed mode. Vsync was also On.

Sincerely,
Tinker missile launcher player guy