I have problems of clumping in the preparation of suppositories with acetylsalicylic acid and paracetamol

When analysing the compound I would extract acetylsalicylic acid as the culprit. In custody, the formation of a certain amount of   acetic acid is unavoidable. With the exception of acetylsalicylic acid I would fine-tune the powders in the correct order and mix it in a small   mortar.. Acetylsalicylic acid is finely made in a separate mortar. On the one hand the powder mixture with a portion of the melted suppository basis is rubbed and on the other hand the   acetylsalicylic acid with the remaining part. Both mixtures are transferred into the Suppository pour jug and gently blended. Then the suppositories can be poured.