We are using latest Azure AD Connect tool (1.1.371.0) on WS2012R2 server (2CPU, 2GB RAM, Hyper-V virtual machine). In a few months synchronization has hanged 3-4 times. I usually reboot whole server to fix this. Today i have found such error (at the same time AD Connect Sync Status tool was showing in-progress state):
The management agent controller encountered an unexpected error. "ERR_: MMS(2084): ..\memutils.cpp(7965): Unusual error code reported 0x80004005 Azure AD Sync 1.1.371.0" The management agent "ourdomain.onmicrosoft.com - AAD" failed on run profile "Delta Synchronization" because the server encountered errors.