Okay - So you have a good idea that the Osprey unit works on your car.
If you are unsure if the cheap cable is effective, then I think you may have to bite the bullet and buy a good quality cable first.
Then when it arrives, identify it as the new cable with some tape and then go to the know good Osprey unit.
Try the new cable first and if it charges okay on that post, then you’re good to go.
Next time you need to charge, return to the very SAME post and try the cheap cable.
If it fails to charge, then you have proved it was the cheap cable and ditch it !.
In the mean time, you have the Granny as a fall back plan !.
A lot of manufacturers don’t supply EV’s with Granny units anymore, because most EV owners have a wall box and because they are slow.
We recently bought a MGS5 which is the replacement for the ZS EV.
It did not come with a Granny unit, it came with a type 2 lead instead.
I insisted on have a Granny unit instead, which they provided.
Will I ever use it ?.
No very unlikely, but they prove invaluable when this type of thing happens and you have a back up plan to hand.
Mine travels with me in the boot.
My brother had a similar problem with his untethered Rolec wall box when trying to charge his ZS EV one day.
Out of the blue,, it just refused to allow a charge and he was low on range.
He called in a panic and asked for some help.
I told him to try the Granny unit in the boot, he was not aware that the car had one !.
I worked just fine, it turned out that water had entered is type 2 plug and the car did not like the moisture it detected.
The box is badly exposed to the wind and the rain.
He replaced the cable with one in the link I sent you and ungraded the type hood that should protect the cable in bad weather.
Everybody had there own favourite between tethered or untethered, my personal choice is 7.5 mitre tethered cable on my wall box and a type 2 cable stored in the boot for public charging ( but never used in anger tbh ).