$page-of(false) causing havoc in frontend

[MSP01]

I have a template file where I need to set $page->of(false) and then save a variable in a field.

This seems to break the frontend, specifically combo fields. Settings the $page->of(true) after saving doesn't seem to do anything either. How to does one fix something like this, or is $page->of(false) something that shouldn't be used inside a template file? I'm pretty sure I've done this a lot in the past without running into issues with it.

Edit:

Some additional information. The saving is done inside a function where the page is passed to. $page->of(false) and $page->save() seem to work fine, but $page->of(true) does nothing. 

I've solved this temporarily by putting $page->of(true) right after the function call, but it seems like bit of a hack.