The game or the driver seems to be having issues gracefully releasing resources, but if the game runs acceptably well when it's being played a lack of VRAM is not likely the issue itself (and the IGP on this part is sharing up to half of the system's memory, which is plenty). Lack of total memory might be, especially if the page file was disabled or made too small for Window's memory management to do it's job.
You might be able to reserve more than that 1GiB default by changing the setting in the UEFI setup (if such a setting is absent, a firmware update may reveal it), but I'm not sure that would help.