Many broadcast type Analog Betacam VTRs have a board to loop the last line, if it is not able to read the coming lines from tape. So it repeats the last good line, until it reads the next good line. This is known as a drop. If the VTR didn’t have that mechanism, you would have a bad video image on those bad lines. And Sony thought that, for small errors, this dropout technique is efficient in cost and quality.
One solution is: if a betacam SP can not read some lines, I expect it to be good in the next or previous field. Since the two fields in a frame are many times very similar; you can deinterlace your frame, and reveal the bad lines of the bad field from the good field in paint module. This works in many cases, if the betacam SP is not too damaged. Because two fields are physically far from each other on tape.
In final, this technique is not an ideal solution, because you loose resolution vertically in the damaged lines, but will seem far better than a dropout.