Missing Time Slots definition in the BSC dump !!

Dear Members,

We are analysing the channels for each cell/TRX on some huawei BSC dumps of our network. We have noted that 3% of our TS were not defined, most of the time TS number 0 of one TRX of the cells.
So in other words, when we analyse TS, TS number 1 is either SDCCH or TCHFR and always defined, TS number 2 is either PDTCH or TCHFR and always defined, etc... except TS number 0 that is missing for 3% of the cells.
Do you know why ? Is it a data fill error or is it a new huawei technical specific configuration ? many thanks for your answers, thoughts and explanation.