Splitting HTML imports into two separate files , imports on 2nd file are not loading

Question

My code is like this ,

index.html

<link rel="import" href="ele/applaunch.html">
<link rel="import" href="ele/applaunch2.html">

applaunch.html

<link rel="import" href="file1.html">
<link rel="import" href="file2.html">
<link rel="import" href="file3.html">
.
.
.
<link rel="import" href="file100.html">

applaunch2.html

<link rel="import" href="file101.html">
<link rel="import" href="file102.html">
<link rel="import" href="file103.html">
.
.
.
<link rel="import" href="file200.html">

After gulp build-prod , when I call index.html , imports of applaunch2.html are not getting loaded . But if I move all import to applaunch.html then everything works fine .

Note - This problem occurs only in vulcanized build (after gulp build-prod) , non vulcanized build have no issues.

Folder Structure - src/index.html

               src/ele/applaunch.html


               src/ele/applaunch2.html

Thanks in advance , pardon me for errors.