There were reportedly bitter disagreements between the Iranian Jafari and the regime and Russian forces
Although the Iranian version of this affair spoke of ending his mission, the sudden departure of Iranian General Ahmad Madani, nicknamed "Hajj Javad Jafari" from Syrian territory last month, was a major blow to the Iranian militia.
The aforementioned commander for years commanded the Revolutionary Guards militia, inheriting it from General Hussein Hamdani who was killed in 2016 in circumstances that have not yet been clarified. Although Tehran insists there were no disagreements (with the Assad regime), but developments on the ground indicate otherwise.
There are also reports that there have been disagreements between Jafari and the regime and Russian forces, particularly over how to deal with American and Turkish forces.
NEWSRAEL: Why this matters
In short - all is not rosy for the Iranians in Syria. The different "powers" there are all vying between each other to reach their aims and those aim are not the same. Accomodation can be made, for a time, but ultimately, most of these aims contradic each other and this is what is happening now.