Assalamu alaikum
I wanted to know if waaw saakinah preceeded by dhamma and yaa saakinah preceeded by kasra are sometiimes tarqeeq and sometimes tarqeeq like alif. If this is so, can you explain when they are tarqeeeq and when they are tafkheem.
Answer
Wa alaikum assalaam wa rahmatullahi wa barakatuh,
The letters
and 
always have tarqeeq and never have tafkheem, no matter which letter precedes them and which letter follows them. Wa assalaam