Black and Gray tank valve hard to pull

[SRD]

I have a new to us, 2012 3100RL 5th wheel we bought end of Sept. When emptying the tanks the black and gray valves inside the convenience center are very hard to pull out when emptying the tanks. It takes both hands to get the valves started and once started the valves will pull out but are very hard to push back in to close. I bought valve lubricant and put in both tanks and it hasn't seemed to help. Any suggestions?
thanks
Steve