pip home assessment

im looking for some claification or if anyone knows the reason why i might be having 2 assessments for pip. I had a home visit in december and they are coming back again in febuary. i am in total meltdown mode and if the first one is anything to go by im dreading the next one. I was so stressed and anxious i could barely control myself but did manage to answer all the questions they asked. I was unable to do the phsyical part as i was in excruating pain that day and explained this to the assessor although she would have seen this by the length of time it took me to open the door. and been able to see how much pain i was in. When i answered the phone (which i dont normally do but was expecting a call back from my doctor)i was caught totally off guard and just wanted of the phone. I was told it was to do a more roboust assessment and that if i didnt attend they would refuse my claim. I asked for home assessment as in my original assessment and they have accomodated this but because i have done this and not went into the centre i would not be able to cancel as the time difference between centre appoitment and home visit was 10days. i just dont understand how they can do 1 assessment and request another before a decsion has been made. Has anyone had this experience and how did they plan for this. Will both assessments be looked at when making my decsion or will they only use one. thanks in advance for any help or support, viv