Sync updates

[pblazej]

Buffer updates are designed to be async, however the properties themselves are not isolated. The use of async keyword creates a suspension point and can change execution context (effectively updating from the thread pool/multiple threads):

which is then clearly visible under Thread Sanitizer:

The current solution is equivalent to main thread updates.
Otherwise, we'd need to block the main thread to swap them and then access synchronously inside draw(), which is probably not worth the effort.