[Bug]: The AMF Decoder Flush method does not flush the decoder completely

[actus-reus]

Describe the bug
Decoding artefacts occur (randomly) at the beginning of a seek although the decoder has been drained and subsequently flushed. (When seeking to new position, a "Drain" is called followed by QueryOutputs until EOF. Then eventually a Flush is called.)

Output of the decoder have been dumped to files and artefacts are already present.

The first I-Frame does not present artefacts but subsequent pictures (Ps & Bs) are. Artefacts on Ps and Bs clearly shows portion of pictures/packets that had been pushed to the decoder BEFORE the drain/flush as if the decoder had retained some internal buffers despite the Flush.

IF the call to "Flush" is followed by a "ReInit" (everything else kept the same), the artefacts do not appear anymore. It therefore seems that the Flush is sometimes not complete.

To Reproduce
Occurs randomly but easy to reproduce with long GOP IBBP streams and rapid seek changes.

Setup (please complete the following information):
OS: Windows 10
Driver Version: 32.0.12019.1028 & 32.12033.1030
GPU: RX 7600
Which component has the issue: AMF Decoder

Debug Log (please upload or paste):

Expected behavior
No decoding artefacts.

Screenshots
In the attached archive file, img_39_xx and img_40_xx are decoder outputs before the seek while subsequent indices are decoder outputs after the seek (i.e. after a drain and a flush of the decoder). img_41_xx is the I-frame that is correctly decoded. Subsequent images are Ps and Bs that clearly show artefacts coming from pictures before the flush.
Archive.zip

Additional context
Add any other context about the problem here.