Knocking sound from left pedal.

More woes...
Can anyone help please with this problem.
I've had a pair of Shimano XT M8120 (maybe the 8020 version) SPD MTB pedals for about 18 months.
Link for general reference https://www.amazon.co.uk/PEDALES-SHIMANO-Enduro-Pedals-Adults/dp/B07SRGC4ZW
But in the last week, the left one has started to make a knocking sound at the 12 o'clock position. And I believe I can feel a "vibration" under my foot too.
The knocking can be heard on the flat and ascending.

I've taken the bike to a bike shop for advice. They say it's my bottom bracket, and it needs tightening up.
I did replace my BB (BBR60) a few weeks ago, because of clicking (not knocking) noises.
I checked the BB and it was tight. But dissembled/reassembled it again to make sure everything was OK.

I have also removed the spindle from the pedal, cleaned it and applied new grease to flush out the old.
Today, on a ride, I thought I'd cured it, but the knocking sound returned.
I don't think the problem is anything to do with my cleats, as I can unclip and pedal with my heal and I still hear the knocking.

Would you do a full dissemble as shown in this YT video or just buy some new pedals, because it's not fixable or related to just cleaning the pedal spindle?
https://www.youtube.com/watch?v=KtOQlEjp9HI

Thank you.