What you are describing is a common phenomenon after breast implants are placed underneath the muscle. As the muscle contracts it will compress the implant and change its shape. It does not indicate that anything was improperly done at the time of surgery. If you feel however that this is a problem for you it is best that U discuss
What you are describing is the result of the lower medial pectoralis muscle pulling on the medial breast where it is attached. This is something that can happen with some but can be corrected unless your surgeon released the muscle too far up the sternum. Conversion to a dual planar type III dissection as described by Dr. Tebbetts could well fix this.
A photo would help to confirm my guess.
See your surgeon for a possible modification assuming they certified by the American Board of Plastic Surgery.
It happens when the implant is of such a size that the muscle pushes down on it when it is flexed. All implants will animate in that way, but some are more visible than others. It is not a sign of anything improper being done. The larger the implant or the wider the implant, the greater chance of seeing it. Also in smaller breasted women to start with that have less of their own breast tissue covering the upper part of the breast it is more easily seen. The only remedy is to remove the implant from under the muscle and place it on top of it.