Thank you for your question, my name is Steve and I am a fully qualified vehicle technician with over thirty years in the trade, hopefully I can help you.
The failure of the rear boot opening system is quite common and as it hasn't been fixed I would suspect it is the power rams, these need replacing as a pair and Are around £800 (estimate I haven't bought any for a couple of years)
The BMW could be put on a diagnostic to confirm, but I am sure that if the fault was anything easy like the fuse, then it would have been fixed already. Another possibility is that the control unit has failed, but the struts are the most likely.
I would certainly factor this into the purchase price.
I hope this answers your question but do please feel free to ask any further details by replying to this thread.
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