Can't find a hit when deleting trailing characters in the address

[Jolly-Pirate]

Here's an interesting behavior (or bug?). Say I'm starting a search for 1Trum with seed 0. It finds it very quickly, since it's a short string.

$ VanitySearch -gpu -stop -s 0 1Trum
VanitySearch v1.19
Difficulty: 264104224
Search: 1Trum [Compressed]
Start Thu Mar 25 13:35:02 2021
Base Key: 853667EC5FC4831F9731AE1B602B7757C712929F1105A987C68A2F27D0A9C757
Number of CPU thread: 1
GPU: GPU #0 GeForce GTX 1650 (14x64 cores) Grid(112x128)

PubAddress: 1TrumrxxCmTobXP4LUkiHnSGoc5jHVcQN
Priv (WIF): p2pkh:L1LPndUmg7zr944oNsc4NhYeVq7XaHVA6SqvaWVZbRq1L6Lsh7XH
Priv (HEX): 0x7AC99813A03B7CE068CE51E49FD488A6F31C4A478193F6B3F9482F64FF8C6C3E

When I rerun the search with the full address 1TrumrxxCmTobXP4LUkiHnSGoc5jHVcQN, no problem, it finds it quickly. But if I delete sequentially the last 5 characters and rerun the search, it doesn't find anything and keeps going forever. Deleting more than 5 characters and down to the initial search string 1Trum, it finds it quickly.

1TrumrxxCmTobXP4LUkiHnSGoc5jHVcQN found hit

1TrumrxxCmTobXP4LUkiHnSGoc5jHVcQ no hit
1TrumrxxCmTobXP4LUkiHnSGoc5jHVc no hit
1TrumrxxCmTobXP4LUkiHnSGoc5jHV no hit
1TrumrxxCmTobXP4LUkiHnSGoc5jH no hit

1TrumrxxCmTobXP4LUkiHnSGoc5j found hit
1TrumrxxCmTobXP4LUkiHnSGoc5 found hit
1TrumrxxCmTobXP4LUkiHnSGoc found hit
etc... down to:
1Trum found hit

This happens with any address, whether searching on CPU or GPU (so it's not related to CUDA). Is it an expected behavior or a bug? Maybe it has something to do with the checksum appended to the double hash functions before converting to base58?