I'm not familiar with Asciidoctor, but this looks like an error in the generation or link syntax in the .adoc files.
There are a handful of cases:
grep -ir '.html.html' .
./docs/05blocks/blocks.html:(<a href="../04debug/debug.html.html#debug_prudebug">prudebug - A Simple Debugger for the PRU</a>)
./docs/05blocks/blocks.html:<p>See <a href="08ai/ai.html.html">Configuring pins on the AI via device trees</a> for configuring
./docs/05blocks/blocks.html:<p>See <a href="08ai/ai.html.html">Configuring pins on the AI via device trees</a> for all
./docs/05blocks/blocks.html:(<a href="../01case/case.html.html#case_rgb_matrix">1.4. RGB LED Matrix - No Integrated Drivers</a>) and want to know
./docs/03details/details.html:<p>See <a href="../04debug/debug.html.html#_dmesg_hw">dmesg -Hw</a> to see how to tell if the PRU
./docs/04debug/debug.html:<p><a href="../05blocks/blocks.html.html#_memory_allocation">Memory Allocation</a> gives examples
./docs/04debug/debug.html:<p>See <a href="08ai/ai.html.html">Configuring pins on the AI via device trees</a> for configuring
./docs/book.html:<a href="../05blocks/blocks.html.html#blocks_pwm">PWM Generator</a> for an example.</p>
./docs/book.html:<p>See <a href="../04debug/debug.html.html#_dmesg_hw">dmesg -Hw</a> to see how to tell if the PRU
./docs/book.html:<p><a href="../05blocks/blocks.html.html#_memory_allocation">Memory Allocation</a> gives examples
./docs/book.html:<p>See <a href="08ai/ai.html.html">Configuring pins on the AI via device trees</a> for configuring
./docs/book.html:(<a href="../04debug/debug.html.html#debug_prudebug">prudebug - A Simple Debugger for the PRU</a>)
./docs/book.html:<p>See <a href="08ai/ai.html.html">Configuring pins on the AI via device trees</a> for configuring
./docs/book.html:<p>See <a href="08ai/ai.html.html">Configuring pins on the AI via device trees</a> for all
./docs/book.html:(<a href="../01case/case.html.html#case_rgb_matrix">1.4. RGB LED Matrix - No Integrated Drivers</a>) and want to know
./docs/book.html:<a href="../05blocks/blocks.html.html#blocks_mapping_bits">Mapping bit positions to pin names
./docs/01case/case.html:<a href="../05blocks/blocks.html.html#blocks_pwm">PWM Generator</a> for an example.</p>
./docs/06io/io.html:<a href="../05blocks/blocks.html.html#blocks_mapping_bits">Mapping bit positions to pin names
For example, on this page the "prudebug - A Simple Debugger for the PRU" link points to https://markayoder.github.io/PRUCookbook/04debug/debug.html.html#debug_prudebug (incorrect) instead of https://markayoder.github.io/PRUCookbook/04debug/debug.html#debug_prudebug (correct).
I'm not familiar with Asciidoctor, but this looks like an error in the generation or link syntax in the .adoc files.
There are a handful of cases: