Operating system: Windows-10-10.0.18362 64 Bits
Graphics card: GeForce GTX 1070 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 431.36
Broken: version: 2.81 (sub 3), branch: fluid-mantaflow (modified), commit date: 2019-08-27 23:26, hash: rB552149d8f537
Short description of error
[made a gas sim with 2 mesh emitters, added another emitter using particles, then only one of the original mesh emitters works / creates smoke]
Exact steps for others to reproduce the error
[Bake the attached sim and view, then enable the 'muted' collection (and probably bake the particles again) and bake the domain again, you should lose one of the mesh emitters if it behaves like it is for me.
I noticed this before with another sim using 2 particle systems as emitters (when the second was added it stopped making smoke from the first), but just assumed this was particles being fairly broken in Blender 2.8x.
Here's my results- https://www.youtube.com/watch?v=iVOlAPERcuY&feature=youtu.be
On the left is the sim before adding the particle emitter, sorry for the low-rez render but sort of gave up when the issue occured...
[Based on the default startup or an attached .blend file (as simple as possible)]