The vertical adjustment operates normally after the RFD is triggered. If vertical adjustment is not needed, R5 can be reset at any time after the RFD is activated.
This CRTC bug divides the CPC demoscene community, with some considering it fully understood, while others find it still perplexing as it seems like the bug itself is bugged.
This effect is used in the [https://www.cpc-power.com/index.php?page=detail&num=19308 DSC4 demo].