"Failed to ready module" but only on homepage

[Studio Lambelet]

I'm working on a page builder module that extends FieldtypeMulti, with the same way of storing data as FieldtypePagetable (field value is a WireArray). I'm using ProcessWire 3.0.200 / PHP 8.1.6.

Everything is working fine on all the pages I use this module except on the homepage (id = 1).

If I try to save a new value on the homepage, the system throws the following error:

Quote

Failed to ready module: FieldtypePageBuilder - Can't save field from page 1: /: Call $page->of(false); before getting/setting values that will be modified and saved. [pageBuild1]

Here is the code used for saving the field value:

/**
 * Add a page to a PageBuilder
 * 
 * @param int $parentForBuilder 	id of page that contains the builder
 * @param string $builderName 		the name of the PageBuilder field
 * @param int $newPageId 			the newly created page id
 * @param string $position 			position to add new bloc, can be: first, before, after, last
 * @param int $prevPageId 			either 0 or ID of page the new bloc should be before/after
 *
 * @return void
 * 
 */
protected function addBlocToBuilder(int $parentForBuilder, string $builderName, int $newPageId, string $position, int $prevPageId) {
	$parentPage = $this->wire('pages')->get($parentForBuilder);

	if (!$parentPage->get($builderName)) {
		$this->exitError(400, __('Could not get builder.'));
	}

	// FYI, $builder is a WireArray
	$builder = $parentPage->get($builderName);

	if (!$builder) {
		$this->exitError(400, __('Could not update WireArray.'));
	}

	if ($position === 'first') {
		$builder->prepend($newPageId);
	} else if ($position === 'before') {
		$builder->insertBefore($newPageId, $prevPageId);
	} else if ($position === 'after') {
		$builder->insertAfter($newPageId, $prevPageId);
	} else {
		$builder->add($newPageId);
	}

	$saveState = $parentPage->setAndSave($builderName, $builder);

	return $saveState;
}

According to the documentation setAndSave "does not need output formatting to be turned off first". So I would not except this error.

I also tried saving with the following code instead of setAndSave(), without success:

$of = $parentPage->of();
$parentPage->of(false);
$parentPage->set($builderName, $builder);
$parentPage->save($builderName);
$parentPage->of($of);

I find it particularly weird that this bug only occurs on the homepage. One more thing that doesn't make sense to me: if I call a bar dump from Tracy Debugger before saving - e.g. bd(wire('user'); saving will success...

I would be really happy if someone could give me some advice, I spent really too much time on this bug. Thanks in advance!