Sounds like my experience with Mangrove Jack's M15 Empire Ale yeast. It's attenuation rate is listed as 71 to 75%, but I consistently see 67% when using it, even with lower mash temperatures. The only way I've managed to get more out of it is by using simple sugars. I love it for bitters.
It looks to me like RVA borrowed most of their strains from White Labs, and a few from Wyeast. Liquid strains that likewise consistently quit attenuating "early" often in the 64-69% attenuation range similar to M15 include WLP002 and WY1968. The latter two are touted as Fullers strains but some folks out there have serious doubts.
Citation of any brewery of origin based solely on Kristen England's ancient listing on MrMalty.com is largely questionable. I don't include source breweries on my own enhanced and constantly maintained list. Using that old data for marketing is of course very unwise for multiple reasons.
I can't be sure why the OP is getting attenuation consistent with those two strains WLP002 and WY1968. as it's obvious RVA borrowed from one of those for a different product RVA 131 Chiswick. Other ideas:
Has calibration of hydrometers and mash thermometers been checked recently?! Worth consideration.
Or how about mash pH? Try mashing at 5.6 instead of 5.3-5.4. Lots of debate out there currently whether the ancient texts were specifying optimal mash pH as measured at room temp vs. at mash temp. There is a real difference in pH between temperatures of approximately 0.20-0.25.
Pitch rate in my experience is overemphasized and doesn't affect attenuation as often feared, i.e., I'm confident pitch rate isn't the problem.
Could also be a mixup in labeling of the slant, maybe the OP received RVA 131 instead of 132 Manchester.