Should under the muscle, silicone implants ripple?

While under the muscle placement minimizes the risk of rippling it is possible in any location. Without examining you it's difficult to know what is actually going on so I would reccomend seeing your surgeon to be examined. Best of luck!  

It is still possible to have rippling even with silicone implants placed under the muscle.  This can happen in the case of capsular contracture, when the layer around the implants becomes too firm and thick, causing implant distortion.  It can also happen if oversized implants are inserted, so the tissue (including the muscle) becomes very stretched out so there is only a thin layer over the implants.

Any implants in any position can ripple.  To a certain extent this is a patient related phenomenon.  If you ripple with one implant, you might have rippling with any implant. Silicone implants come pre filled, so they cannot be under filled.

Any type of implant, placed in either location MAY ripple.  It isn't really a complication, but really a limitation of the procedure. The most likely situation for ripples` to be seen is with textured, above, saline, in a woman with minimal tissue.  However, ripples may be seen even in ideal candidates, who have minimized chances.  This can result in under-filling saline implants, or the capsule itself.Silicone implants are never under or over-filled.  They are filled and sealed at the factory and can't be adjusted.sek

Yes, any type of breast implant, placed in any "pocket" can be associated with rippling and/or palpability.   Generally speaking, palpability and rippling of breast implants may be related to several factors. These include the amount of soft tissue and breast tissue coverage over the breast implants, the position of the breast implants (submuscular versus sub glandular), the type of implants (saline versus silicone), and the degree of overfilling of saline filled implants. Generally, weight loss will extension weight any rippling/palpability of the implants. Deflation of the implants will also increase the rippling/palpability of the implants.
Correction of the rippling may involve further surgery including implant pocket exchange if possible ( sub glandular to submuscular), implant exchange if possible (saline to silicone), and/or the use of allograft to provide an additional layer of tissue between the implant and the patient's skin. Patient weight gain (if possible) may also be helpful.  I hope this, and the attached link, helps. Best wishes.