[Giuliano Bausano] “32Gb, 4 hours video”
That should have been your first clue that no way was that ProRes, in fact I don’t even know how that is a 4 hour HDV, which is about 12-13GB/hr. That sounds like a delivery codec and not HDV (which is a favor of mpeg2)
If it is not HDV I would convert the footage. I don’t work in HDV much but when I do I convert it to ProRes before I start.
If you convert you movie and name it exactly the same, then rename the original name(HDV). When you reopen the project it will load the ProRes and then you change your compressor setting of the sequence to ProRes.
Always backup the project file before starting.