Thanks for the review.
Shadowsun was originally a metal model which was recast in GW resin (not FW resin which is of a far higher quality) using the old metal moulds.
GW resin (Finecast - or Failcast depending on your point of view
) suffered from casting errors and general poor quality although I do not know if this problem has now been resolved but it looks like your model was not the best of casts.
Being resin, standard plastic glue will not work and you will have to use super glue or an epoxy glue and make sure that all traces of mould release agent are removed by cleaning with soapy water. It seems like the shield drones may be fully plastic so the standard plastic glue will work there.
from the GW website with my underlining
This is a finely detailed resin cast kit, and contains fifteen resin components, fifteen plastic components, four long flying stems, three small flying bases and a sprue of four 25mm round bases, all of which make Commander Shadowsun as well as 2 shield drones and a command-link drone.
This kit is supplied unpainted and requires assembly - we recommend using Citadel Super Glue and Citadel Paints.