What is cause of my timeseries data assignment error please

NaN should correspond with data type single but isn't accepted - see below. -------------------------------------------------

>> get(t.Force_01) % produces answer below

ans =

               Events: []
                 Name: 'Force_01'
             UserData: []
                 Data: [90750x3 single]
             DataInfo: [1x1 tsdata.datametadata]
                 Time: [90750x1 double]
             TimeInfo: [1x1 tsdata.timemetadata]
              Quality: []
          QualityInfo: [1x1 tsdata.qualmetadata]
          IsTimeFirst: 1
    TreatNaNasMissing: 1
               Length: 90750
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>> t.Force_01.Data(81812,3)=NaN %produces error below
Subscripted assignment between dissimilar structures.
Error in tscollection/setts (line 157)
             this.Members_(I(1)) = x;
Error in tscollection/subsasgn (line 9)
         varargout{1} = setts(h,thists,S(1).subs);
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NOTE
>> t.Force_01.Data(81812,3) % this shows the structure is nothing special
ans =
   -1.4650
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The assignment works with small example below even though structures are the same as timeseries 't' (I think).
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A = timeseries([1:3; 4:6],'Name','A');
B = timeseries([7:9; 10:12],'Name','B');
tscAB = tscollection({A B}, 'name', 'tscAB');
clear A B;
tscAB.A.Data(1,1)=NaN;
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