It sounds like you're publishing your site as precompiled and not updatable:
Precompiling Your Website (C#) | Microsoft Learn[
^]
The compiler seems to think your RDLC file is a page to be compiled, so it gets compiled into the
.dll
, and the file is replaced with a marker.
According to
this SO answer[
^], you need to set the build action to "content", and remove the RDLC build provider from the web.config file:
<buildProviders>
<add extension=".rdlc" type="..." />
</buildProviders>