Erdogan ISIS
With dozens of armed groups involved, the Russia-US brokered ceasefire in Syria was never going to be easy. But amazingly, the ceasefire is largely holding. Of course, there's always a few party poopers:
A Russia Defence Ministry center in Syria received reports on Saturday of Turkish shelling of Kurdish positions in Syria's Aleppo province, RIA news agency reported, while Turkey said it had been targeting Islamic State positions.
Were the "ISIS positions" in Turkey?

Rhetorical questions aside, Turkey's decision to exclude the Syrian Kurds from the ceasefire could have severe repercussions for the entire peace process. And Moscow is worried:
Russia has called on Turkey to stop actions that could torpedo Syria's peace talks and disrupt the ceasefire in the war-stricken country.

Russian Deputy Foreign Minister Gennady Gatilov on Friday slammed Ankara for shelling Syrian Kurdish positions and for sending weapons across the border to assist foreign-backed militants, Bloomberg reported.

Such actions must stop "to provide a more constructive atmosphere for the intra-Syrian talks and a more durable ceasefire," said Gatilov.
Simply put, Erdogan gains nothing from the ceasefire: Turkey is heavily invested in toppling Assad, and the Syrian government has already made it clear that only elections, and not backroom deals, will remove him from power. Furthermore, the Syrian Kurds now control a huge swath of northern Syria -- territory which was once held by Turkey's "moderate rebels". In other words, if the ceasefire holds, Erdogan's proxy armies will never be able to take back northern Syria. And of course, without controlling northern Syria, Turkey's dream of a "buffer zone" would not be achievable.

Even the US seems eager to reach a peace settlement in Syria (probably so it can move on to its next target?).

Erdogan has gone rogue.