DLA payment and PIP payment

Hi all
recently my husband was awarded pip from dla
my question is he received a dla payment on the 31st of january and his next payment was due on the 28th feb, meantime we had a letter from pip to say his award for dla will end 14th feb and pip will start four weeks after the award was given which was 20th jan, we then received a dla payment of 158 pound which is two weeks dla on 14th feb, we will only be getting the first payment of pip on the 14th march, is this correct as i really am confused by the whole thing, sorry if my question is confusing,

We see this quite often. Most people find that payments work out once PIP is established.

took me 2 weeks and 3 calls to get my head around change over payments but all worked out

I can not understand this I was getting DLA . That was stopped and a questionnaire sent to me. No examination or face to face . So as I had recently moved and had problems finding paper work.
In that paper work I had a medical certificate stating I was permantley disabled at least to well after normal retirement age. that was followed with messed up treatment for Cancer and a reassessment for IIB which confirmed still 20 % disability in Lower limbs.
The IIB did not consider Cancer but I did qualify for IIB.
Now I have had to contact my MP and the head of the DWP in London Noel Shanahan who has apologised for holding the wrong information some one invented a non existent Pension.
I was investigated by F&E but they then not only said I was in no way remiss but DWP had lost my DLA records.
I started a new claim in July last year after fighting all of that mess up . I Got a home visit and as it was a Capita Assessor and it was Capita that had issued my Medical certificate which I had kept a copy of as I had intuition having been a civil servant there was an award of PIP!
But it was only back dated to the date of my new claim last July.
So DWP have been allowed to loose records and not only do I loose my mobility but lose DLA from August 2014 to July 2016. So my life has been very much effected by DWP mistakes.
Now I have to be reassessed for IIB. Even though I am in the support group for ESA and now have a PIP but lost Two years! Why is IIB different. My lower limbs can not be fixed !