BlockingQueue VS Examples

This post was the inspiration for this TLA+ tutorial: https://github.com/lemmy/BlockingQueue

I need to write a small case study using TLA+. Where can I find some distributed/concurrent algorithm or system that is not too complex and hasn't been specified yet? There are so many examples already covered in the official repository alone that I'm out of ideas.

However, for example, Lesslie Lamport elegantly modeled distributed transactions without introducing the concepts of events or messages, focusing only on the state of the participants.

I am very new to TLA+ and I am trying to learn it through the book Specifying Systems by Leslie Lamport. I am currently working on the InnerFIFO example from Chapter 4. I attempted to use the TLC model checker on this example. So, I created a new model and specified the following value to the constant Message - {"hello", "world"}. Upon running the model checker I get the following error -

I did not use Pluscal. I did have to EXTENDS TLC to use the Print function, based on this example: https://github.com/tlaplus/Examples/blob/master/specifications/SpecifyingSystems/AsynchronousInterface/PrintValues.tla

Adding a vector clock is relatively straightforward (see e.g. https://github.com/tlaplus/Examples/commit/ee10c6ed1c65f1002c8ad402edceeffcf1a833e). For PlusCal, the vector clock can be computed from the PC variable: https://github.com/tlaplus/CommunityModules/blob/master/modules/ShiViz.tla

The TLA+ github has several examples.

I found this here as well: https://github.com/tlaplus/Examples/tree/master/specifications/SpecifyingSystems/CachingMemory