Is the PS at Fault if my Implants Go to Far Towards/Under Armpits? (photo)

without more information , an anser is always difficult..   it appears that your implants are quite large and your breasts may have had some sagging.  the pocket can enlarge with big implants even if it was made correctly.

you will probably need to have the pocket reduced.  maybe smaller implants,  maybe a lift if you want your breast higher

Thank you for the photos. You do not state what size implants you have. Looking at the photos, they are too large for your chest wall, so it is not a surprise that they slide off laterally. In the supine position they go lateral as any woman's large breasts would do.  In the upright positon, they seem a little low, leaving your upper chest flat without a bra. Now it could be malposition or most likely your tissues are not elastic enough to support these large implants and the skin envelope is stretched by the weight. The only "fault" your PS could've committed is if he/she did not discuss with you your anatomic limitations in placement of large volume implants and their consequences.