Scrapping in empty but retooling shipyard

[Detros (OP)]

Military shipyard with 2 slipways of 5500t size, both of them currently not doing anything is retooling itself to a new design.
Yet it seems I can't use it to scrap 5500t commercial ship in the mean time. Is the problem in military/commercial type or that it is currently retooling? I thought both type and complex activity were irrelevant and only empty slipways and their size mattered.

[davidb86]

I have found that I can modify a shipyard (retool, capacity expansion, or add a slipway) if all of the slip ways are busy, but once I start a modification, I cannot then add construction, refit or scrap tasks until the modification is complete.  I  do not know if this is an error or the intended design.