Jonas Buccholz wrote:   I have not been able to find any consistent pattern when l becomes retroflex 
 and Anna Esposito wrote:  So far, no one has been able to explain to me why the l has been 
changed to ḷ in these words, and consistently in every manuscript (and 
also in the printed edition). 

I also don't see a pattern. For example this sentence from the manuscript I'm looking at:

दळाग्रे हां सूर्यमण्डलाय नमः। Why दळा . . . but . . .ण्डला. . .
Harry Spier