Fast forward controls and "Time to next event..."

[brazil]

I recently upgraded from;

Ubuntu/Zoneminder 16.04/1.32 -> 18.04/1.34.16

I followed the instructions and the upgrade seemed to go smoothly.
Overall, I am pretty happy but I'm having some problems with the controls when replaying events.

When I first enter the Event Viewing page and hit the "Fast Forward" control to increase the speed
from 1X to 2X. With this, the fast-forward speed increases accordingly (and the speed drop-down
value is updated with 2X)... GOOD!

If I hit the "Fast Forward" control a second time to increase the fast-forward speed to the next
level (4X?), the speed appears to increase according to the video time, but the replay speed
drop-down goes blank (white).

At this point, the video-playback screen typically goes black with an error stating "Time to next
event = <epoch time> seconds".

The <epoch time> is in the range of the video's timestamp but actively decrementing every
second.

I can force it to return to the video if I change the codec dropdown to a different value. But
revisiting the fast-forward controls triggers the "Time to next event..." error again.

I don't know whether these issues are associated with each other.
I've read some reports of similar problems with prior Zoneminder releases which evidently have
been corrected. But I'm not finding anything on 1.34.16.

At the least, is there a way to mitigate the "Time to next event = <epoch time> seconds" issue. It seems
like a timing/streaming issue. I did check the database integrity and Timezone settings.

I can reproduce this on:

Firefox 78.0.2 (64-bit) OSX 10.13.6
Seamonkey 2.53.2 OSX 10.13.6
Safari Version 13.1.1 OSX 10.13.6

Any pointers to documentation/previous posts or workarounds greatly appreciated.

TIA

[brazil]

Ah, I see, said the blind man. In order for all of this to work mostly correctly, you need to be using a Source Type of ffmpeg. I was using Remote which I was carrying over pre-upgrade.