Operating system: windows 7 sp1
Graphics card: gtx660
version: 2.80 (sub 74), branch: blender2.7, commit date: 2019-06-09 21:43, hash: 030c7df19da9, type: Release
build date: 09/06/2019, 17:18
Short description of error
Exact steps for others to reproduce the error
It is simple to recreate, open blender, save the file, assign a psys to the default cube and write it to disk.
Create another cube, add a psys and set it to external cache playback.
Browse to the external cache and Blender can't read the particles it just wrote to disk, or Blender reads only the particles cached on the first frame.