There is some escalation going on in the southern/south-eastern Syrian desert which is not included in any of the 4 de-escalation zones.
During the last 4-5 months US-backed rebel groups coming out of Jordan have conquered large swaths in the almost empty Syrian desert from ISIS, including the al-Tanf border crossing between Syria and Iraq and reaching the outskirts of Deir ez-Zor province:
https://en.wikipedia.org/wiki/2017_Southern_Syrian_Desert_campaignBut now the Syrian Army and allied Iranian/Iraqi proxies have launched an offensive towards the al-Tanf border crossing, against the US-backed rebels. trying get control over the entire Damascus-Baghdad road:
https://en.wikipedia.org/wiki/2017_Baghdad%E2%80%93Damascus_highway_offensiveThis has the potential to grow into something bigger, with the US trying to connect Jordan to Turkey and Iraqi Kurdistan via Deir ez-Zor province and Syria and Iran trying to reestablish the Damascus-Baghdad road, probably with Russian backing.