I replaced all the copper in my home with pex in 2008. I have had a seepage leak on one of my hot water fittings. I took it apart and cleaned all the parts and reconnected it, and still the seepage. Does that indicate that the manifold needs to be replaced??? I read some about dezincification, would that be my problem?? Since it is one of the top fittings, most of the manifold is blue with corrosion. I cleaned some with my copper pipe cleaner, and it cleans well. Can the pex fittings be damaged by cleaning and does hot water possibly accelerate dezincification??
It would be ideal to know what kind of connections you have on the manifold. Often the connectors can be replaced but it kind of sounds like you don't have that option (or why would you ask?).
So, if you have barb connections, then yes, you have to be careful cleaning them... scratches cause problems. But if there is enough length on the barbed connector for two clamps or rings, that might work. You would want to put the rings adjacent to each other on the pex, and use the crimp tool to crimp them at different angles. Or use a different crimps or clamps like ULTRA-LITE COMPOSITE HANDLE CRIMP TOOL FOR STAINLESS STEEL PEX SLEEVES or Apollo PEX Cinch Clamps.
I suppose that if you had flare nut style fittings, it would be obvious that you could replace the parts, so there's no sense in my mentioning it any further.
Alternatively, if you have a shark-bite style connection, the tube support liner is what usually needs to be replaced. You should be able to remove the support line insert and replace it (depending on the manufacturer). Here's a link for pdf instructions from Shark Bite: http://www.sharkbite.com/sharkbite/wp-content/uploads/SB_Inslltn_Instrctns_2014.pdf
Here's a screen shot image of a google search for generic tube support liners for shark bite style connectors: