Is there any reason al pi halacha to not be mafsik between the Kaddish said after Ashrei before Mincha or the Kaddish said before Mussaf (on Rosh Chodesh or on Shabbos) and Musaf. Please provide any sources.
Answer:
The Levush (cited in Magen Avraham 292:2) writes that one should daven straight after kaddish, and explains that this is the reason why kaddish on Mincha on Shabbos is recited right before the Amidah prayer, and not straight after the Torah reading, like it is during the week (this is also based on the Pardes; see also Ketzos Hashulchan 91:4).
This suggests that although it is not prohibited, one should not interrupt between kaddish and the Amidah prayer, but should rather go straight into prayer from answering kaddish.