[Razor12911]

if not IS7ZipExtract ( 0, 25, ExpandConstant('{src}\data1.7z'), ExpandConstant('{app}\'), false, '') then break;
if not ISSRepExtract ( 0, 25, ExpandConstant('{app}\data1.srep'), ExpandConstant('{app}\data1.pcf'), true) then break;
if not ISPrecompExtract ( 0, 25, ExpandConstant('{app}\data1.pcf'), ExpandConstant('{app}\data1.arc'), true) then break;
if not ISArcExtract ( 0, 25, ExpandConstant('{app}\data1.arc'), ExpandConstant('{app}\'), '', true, '', '', ExpandConstant('{app}'), notPCFonFLY {PCFonFLY}) then break;

7Zip can contain more than 1 file.

and there might something wrong.

when compressing

7Zip > Precomp > Srep > Arc

when decompressing it has to be in reverse

Arc > Srep > Precomp > 7Zip

The steps either compressing or decompression may be incorrect.

I suggest to replace 7Zip with Arc