I encountered the following scenario:
Wyll was killed.
Wyll succeeded a death saving throw.
Wyll received 2 piercing damage (caused 1 failed death saving throw)
Wyll failed a death saving throw.
Wyll succeeded a death saving throw.
At this point I see (in the UI indicator) 2 failed and 2 successful throws as it should be.
Wyll succeeded a death saving throw.
At this point Wyll should have 3 successful throws.
What I see in the UI indicator is 0 successful and 2 failed throws. Wyll is still on the ground.
I let another turn pass and only than do I see 3 successful (and 2 failed) saving throws in the UI.