Woofer pumping WHY??

Hello All, I have an older REL B2 series. I love this sub. I recently received a new Project Xtension 10 with Clear Audio Maestro Ebony v2. After a couple days I noticed bad woofer pumping on several records I like to listen too. When I brought it up to Needle Doctor they told me it was my records and said it worked fine in there store. Now my REL is blown! I am so upset at myself for not taking this matter more seriously. Now I am purchasing a KAB rumble filter because I am not going through this again. Is this a cartridge mismatch?? Because on my REGA with Dynavector 10X5 It did not do this woofer pumping nearly as bad. AND I do remember putting a DENON DL103 on my RB301 and this same woofer crazy action occurred!! Immediately took it off that arm. I just spent $4100 for this Xtension10/CA Maestro and now I am scratching my head. Hmmmm.