sanke keg mystery

Kegging a 10 gallon batch tonight was very confusing! The first keg no problem at all. The second (brand new to me) sanke keg was very difficult to push down the coupler lever. Mind you this is a sierra nevada keg with an american "D" style fitting and a "D" style coupler. The flow stopped completely when the coupler was fully pressed down and engaged. The only time I was able to get a flow at all (but very finicky) was to half press down the coupler lever. Taking the coupler off of the receiving keg covered the floor in beer (flow just fine through fermenter keg/line/transfer coupler). After about a half hour of this and a 1/4 full keg I gave up! Any ideas? I took apart both kegs and looked at the spears/fittings to make sure nothing was clogged or weird with them and I could detect nothing....

Ideas/suggestions/smart ass remarks?

Any keg system experienced folks want to take a stab at this issue??

Did you take the check ball out of the coupler ?

Absolutely! This is just a new keg, not a new system or process. I am stumped here!! Any help?

...so you fill it with the spear in the keg? and use a coupler with the check ball removed?

How do you deal with the potential pressure in the keg you're filling? ...pull the gas check out too?

I always just remove the spear when cleaning , fill without the spear, and then install the spear and seal.

I have always put the spear back in after cleaning, to keep a closed system from fermenter to keg. The receiving coupler has the beer side check valve pulled out and then I have done both manually pulling the pressure relief valve during filling(in an attempt to have a counter pressure transfer(spunding valve would be nice here...)) and just removing the gas side check too.

I'm so confused how fully engaging the lever of the coupler down completely shuts off any flow and feels really hard to push down!!!

I have now beer trying to transfer this beer from primary to keg for almost a week now!!! Any ideas or should I just give up on this keg???

Are you absolutely sure it's a type D keg/spear?

Yes, positive. Its a sierra nevada keg and the spear look identical to the other handful of american D style kegs I have. Certainly not the euro style S with the deeper spear needing the longer coupler.

I guess I'm gonna try to find another spear to drop into this keg...

Broken spring in the spear????New threaded spear type??? Broken coupler???
Is there gas on the keg now, possible over pressure??? Sounds like somethings broken to me.