same thing happened to me . I bricked two MacBooks doing this ( one 5,5 the other 5,1 and both were sst chips) but the solution described above worked for me two. sometimes the clips can be finnicky but eventually I got solid connection and flash recovered my machines. In my case tho the refreshing took 4 hours but they both sst so maybe that was it . I flashed a spare mx chip for an experiment and the only took fraction of the time so go figure. All I can say is be patient and persevere and hopefully you'll be back up and running soonFirst before you continue with what I have to recommend, can you pull your drive, plug it into another Mac and navigate to the Documents folder you were logged into while flashing? If so you can find your backed up rom, and open it with Hex feind. To make sure it's not all garbage search for "SSN" your macs serial number will appear. This will tell you the backup was most likely good. Even if it's not the 09 mini doesn't have ME Region (Core I series and later do) meaning a rom can be created from scratch. If the rom is good you need to purchase a ch341a (https://www.amazon.com/gp/product/B01I1EU9LG/ref=oh_aui_search_detailpage?ie=UTF8&psc=1) and SOIC 8 clip (https://www.amazon.com/gp/product/B00V9QNAC4/ref=oh_aui_search_detailpage?ie=UTF8&psc=1) I swear by mine it has saved me 3 times already. Anyways did your mini freeze while flashing? that happened to mine. I had to reflash it using the ch341a, it took 30 minutes to flash.
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