Loop breaks after certain amount of iteration - php

Question

I've a job to do some migration on wordpress sites, although I don't think wordpress has anything to do with my problem.
So I'm getting a set of data from a table (id, value) which is serialized.
I want to put the serialized data into arrays, according to the function. The algorithm doing everything fine for the first 86 records.
If I run the algorithm on just 86 records I get all the right data instantly. But when I run it 87 or more times its just goes into loading. Doesn't matter how long the max execution time limit is it's still gonna reach it apparently.
I checked the 87th record if theres something odd with it, but nothing i can see. Is there any idea what could couse this?
Here's the code:
global $wpdb;
$houses_built_years = $wpdb->get_results('SELECT post_id, meta_value FROM bp100_postmeta WHERE meta_key = "epites_eve"');
foreach ($houses_built_years as $house_built_years) {
if ($house_built_years->meta_value) {
$years = unserialize($house_built_years->meta_value);
} else {
continue;
}
$build = array(array());
$series = 0; $year = 0;
while (count($years)) {
if ($build[$series][$year] && (min($years) - $build[$series][$year] == 1)) {
$year++;
$build[$series][$year] = min($years);
unset($years[array_search(min($years), $years)]);
} else if ($build[$series][$year]) {
$year = 0;
$series++;
$build[$series][$year] = min($years);
unset($years[array_search(min($years), $years)]);
} else {
$build[$series][$year] = min($years);
unset($years[array_search(min($years), $years)]);
}
}
$repeater = array();
foreach ($build as $series) {
if (count($series) > 1) {
$repeater[] = $series[0] . ' - ' . $series[count($series) - 1];
} else {
$repeater[] = $series[0];
}
}
}
Here's some example of records (algoithm breaking at id = 30517):
30279
1201
epites_eve
a:1:{i:0;s:4:"1898";}
30338
1202
epites_eve
a:1:{i:0;s:4:"1891";}
30397
1203
epites_eve
a:1:{i:0;s:4:"1894";}
30517
1205
epites_eve
a:1:{i:0;s:4:"1897";}
30577
1206
epites_eve
a:1:{i:0;s:4:"1891";}