Several factors contribute to the mystery:
While a 1,100+ episode list is impossible to compile for the Tagalog dub (since the later seasons were never dubbed), here are the most famous cases that aired in the Philippines with Filipino voice acting:
The "Pilot" Arc (Episodes 1-2)
The Billionaire Birthday Murder (Episode 3)
The Valentine Special (Episodes 6-7)
The Moonlight Sonata Murder Case (Episode 11)
The Luxurious Liner Murder (Episodes 22-23) detective conan tagalog episode list
The Haunted Ship & The Kaitou Kid (Early 70s)
The Shrinkage Reveal Attempts
Aside from the TV series, the first Detective Conan movie dubbed in Tagalog was Movie 4: Captured in Her Eyes. It aired on GMA 7 twice and is the only full-length feature officially dubbed into Filipino.