... It doesn't matter who is the source master, first one attempting to add 3rd source point doesn't work, but the next one does.
This contradicts your first post. There you said "... also of Almira ... it didn't give any more source point..." So I guessed first you were heading for Almira after being in the elven camp with Saheila, didn't you?
And It seems not to be restricted to Saheila (and Almira?). As RedPrinceFromHH wrote it also occurs with Ryker.