weak cellano antigen?

Hey everyone, i have a bit of a question here.

Are there weak/partial cellano variants?

we currently need to continuously supply a patient with KK + anti-cellano with units and ran into an oddity:

One of our units tested negative for the cellano antigen in multiple runs, but also tests positive in other runs. If done in traditional IAT in glass tubes the reaction is weakly positive but shaking the tubes even for a short duration causes the reaction to go away. Some antisera give up to 2+, others only (+) to 1+. About half of our runs were negative.

The antisera should be fine since the batch of units we tested included all cellano-positive units except this one weird one. The controls have consistently been fine, too.

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Any of you heard of something like this?