It looks like you are attaching the JLCR tether to the shock cord in a way that prevents it from acting as a streamer, and also transmits the aerodynamic loads of folded chutes air resistance through the tether.
I'm glad it works well for you, but this appears to be contrary to the JLCR tethering recommendations:
View attachment 465730
https://jollylogic.com/wp-content/uploads/2015/12/JollyLogicChuteReleaseWeb.pdf
If you are happy with what you've got, and it's working well, don't change a thing.
Alternatively, I attach the tether to one of chute shroud lines (in slides down to the swivel once chute opens), allowing the folded chute to separate from the shock cord and act as a mini-streamer. This way it is always oriented perfectly for opening, regardless of which airframe element is leading the descent, or if the entire stack is coming in horizontal (happens with one long rocket).
You are not the only one flying JLCR, and your experience is inconsistent with mine.
Perhaps there is something unique to how you attach and tether your JLCR?
The speed of descent should have no effect on chute opening. Period. If the airframe is falling way too fast, the chute may open and shred, but it will still open.
By following JLCR chute packing and tether attachment instructions, I can't visualize a situation that you match your error condition.
YMMV,
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