Not sure if this is the same issue, but may be related.
Running JTAlert 2.16.6 and just installed WSJT-X v2.2.0-rc2.
Not every time, but it will sometimes clear prior calls between decode passes for the same cycle. I will usually see all the decodes in the last cycle, but sometimes it only displays the last few.
Here's screen grab of this. Note that JTAlert display starts with KO9A but above you see 3 additional decodes prior to that call.
Hope this helps