remove cracking thermal cob layer before applying new, sandier thermal cob mixture ?

hello,
i put a thermal cob mixture on the bell and the barrel of my heater that i think has too little sand (because i didn't want to run out of sand before the job was done).
i removed large cracking pieces and reapplied a thermal cob mixture containing more sand on the barrel and it seems to be ok (haven't used the heater yet this season).
i patched the dozens of hairline cracks in the thermal cob layer on brick sides of the bell with the sandier thermal cob mixture. however, cracks re-emerged as it dried so i'm adding more sand to to the thermal cob mixture.

how wise would it be to remove all the existing thermal cob from the sides of the brick bell before applying the latest, sandier batch of thermal cob VS. patching over the existing cracks?
thanks