Web viewer reserves memory for each record view and that memory consumption remains even after closing file or changing layouts. After an excessively long period of time, the FileMaker client slowly releases reserved resources.
How to replicate
Create a new file,
add web viewer object for google maps to form layout,
save layout changes,
enter browse mode,
create record multiple times (to simulate moving through records in a populated database),
If you create, or navigate through, enough records you can fairly quickly generate an out of memory error and crash FileMaker.
Do not use the web viewer object, point to resource heavy websites, or navigate through records on a layout using a web viewer.