S211 new Airsprings exploded - alternatives?

[MercedesClassic]

So my E320cdi estate 2007 avant-garde I've had 9 months 12000 miles now on 135k started to sag in rear end. Indy diagnosed leaking airsprings, would rise then fall overnight.
I bought cheaper airsprings to the OEM or Arnott models, bought from eBay from what looks like reputable albeit non OEM maker or supplier.
Got then fitted on Friday. Car sat and drove lovely was well pleased. Until yesterday out on a roadtrip the tyre warning popped up in red. Checked tyres all fine reset monitor. Car was to go tomorrow for alignment as front suspension refresh has knocked it off and ESP and tyre warning pops up.
Pulled over to let a car past and we could hear hissing noise like puncture. Got out and tyres valves ok but sounded like drivers airspring leaking or venting. Got back in, bang it blew, immediately the other blew and arse hit the road.
So it will go back to Indy in morning. I'm absolutely demoralised, so fortunate it didn't happen when driving as I think it would have been disastrous.
So the argument will be was it faulty parts or wrongly fitted?
Sounded to me that the compressor was working overtime and overinflated them but am I right and if so why?
I'm at the stage that I want steel springs put in if an option?
Help I'm ready for the asylum!

[MercedesClassic]

I ended up buying MB units, exchanging the old for new and 15% discount helped bring price down. Got 4 new tyres and alignment done so she's driving beautifully.

eBay sourced parts that failed I took pics of then refunded me without having to return faulty units. So beware buying cheap parts especially if they compromise safety. If they had blown out whilst driving I shudder to think what could have happened.

I'm hoping for no more bills in next while. Happy motoring.

[donkmeister]

Dare I ask what the damage was for 4 OEM airsprings, fitted? My W211 hasn't thrown me a big bill for a couple of years so it's good to have an idea of what may be yet to come!

[MercedesClassic]

Just seeing your question now. So my estate only has airsprings in the rear. Thankfully! The pair I bought from MB were £640 in exchange for the old units, seemed to be originals.

I'm in MB club so typically get 10% at MB Belfast but this time they gave 15% which was most welcome. I've been a frequent visitor to them in the past year! Mostly for SL55 parts.

The OSF spring also broke just before she went into get fitted but that was more £50. Hence my original question in despair about changing rear out to steel springs and being done with it.

If you need a refresher then Arnott are an option but they seemed very expensive in comparison to the MB units. Maybe with a voucher code etc might be ok.

The eBay sourced units were less than half the price but they literally exploded. Fortunately I had pulled over to let an incoming car past. If this double blow out had of happened on a fast twisty road I dread to think what would have occurred. As it was the bangs nearly killed us with shock.

I'll see if I can upload pics of them. Looked literally like Welly boots inside. Poor construction. The vendor who I believe is Hong Kong based but trades with plenty of Union Jacks on his profile has a very good rating. I couldn't find ratings for the parts nor a way to leave a rating. I'd love to give them my rating!

After quite a few emails back and forth looking for photo and video evidence and me constantly asking for a refund as I'd replaced the parts they kept trying to send replacement units!
Parts were warrantied for 2 years and 30 days exchange or refund which I reminded them of and promptly got refunded.

I hope you get sorted.