Media Player Classic Home Cinema MPC-HC 1.7.13 media progress bar does not progress linear but has big time-jumps

rOS 0.4.7RC1 (I noted this for 0.4.6 & 0.4.5release tests already)

VBox (confirmed also for 4.3.12) + VBEMP + inbuilt Mesa + AC97 from rapps

Observed result
react.log
video.webm

Expected result
The progress bar moves linearilly, like on xpsp3.webm

eventually related to CORE-12227?