Usually this means the parts weren't cleaned and cured properly. At least that's my experience from printing stuff for myself. I would get some IPA and a toothbrush, preferably one you are not using for your teeth, and scrub it, rinse it, dry it thoroughly, and put it in a sunny window for 30 minutes or more. Repeat the process if it still feels sticky and soft. If it's not sticky, but still a little soft, leave it in the window and check it periodically. When it feels good to you remove it from the window. If it stays soft then it's likely to be bad resin or very flexible resin. Hope this helps.