Strange things going on with his shop list as below:

Perhaps he is not supposed to sell the Western Thera map but why does it get replaced? Weird ...

Dolansten's Map Making
up]
Jeril Dolansten the chartmaker sits, carefully looking over documents.

* WE HAVE 6 MAPS *

> list
The shop's hours are 5 AM until 8 PM.
The shopkeeper will purchase: treasure map artifact parchment pen

Item (Type)
< 1 24> a map of Western Thera (map)
< 1 24> a map of Eastern Thera (map)
< 1 24> a map of Hamsah Mu'tazz (map)
< 1 24> a map of Eastern Thera (map)
< 1 24> a map of Mierka V'Dramir's Pirate Cove (map)
< 1 12> a map of Arkham (map)
<15 276> a curved wooden pen (pen)
< 5 72> a thick piece of ecru parchment (parchment)

Jeril Dolansten tells you 'Nothing but the finest for my customers!'

> buy 1.
You haggle the price down to 22 copper.
You buy a map of Western Thera.

> buy 2.
You haggle the price down to 22 copper.
You buy a map of Hamsah Mu'tazz.

> buy 3.
You haggle the price down to 21 copper.
You buy a map of Mierka V'Dramir's Pirate Cove.

> buy 4.
You haggle the price down to 11 copper.
You buy a map of Arkham.

> buy 5.
You haggle the price down to 238 copper.
You buy a curved wooden pen.

> buy 6.
You haggle the price down to 64 copper.
You buy a thick piece of ecru parchment.

*** WE HAVE 2 EASTERN MAPS **8

> list
The shop's hours are 5 AM until 8 PM.
The shopkeeper will purchase: treasure map artifact parchment pen

Item (Type)
< 1 24> a map of Eastern Thera (map)
< 1 24> a map of Eastern Thera (map)
< 1 24> a map of Mierka V'Dramir's Pirate Cove (map)
< 1 12> a map of Arkham (map)
<15 276> a curved wooden pen (pen)
< 5 72> a thick piece of ecru parchment (parchment)

Jeril Dolansten tells you 'Nothing but the finest for my customers!'


> buy 1.
You haggle the price down to 21 copper.
You buy a map of Eastern Thera.

> list
The shop's hours are 5 AM until 8 PM.
The shopkeeper will purchase: treasure map artifact parchment pen

Item (Type)
< 1 24> a map of Eastern Thera (map)
< 1 24> a map of Mierka V'Dramir's Pirate Cove (map)
< 1 12> a map of Arkham (map)
<15 276> a curved wooden pen (pen)
< 5 72> a thick piece of ecru parchment (parchment)

Jeril Dolansten tells you 'See anything you like? A lucky thing you came along.'

> buy 1.
You haggle the price down to 21 copper.
You buy a map of Eastern Thera.

<649/649hp 890/890m 566/566mv <8 AM> 12768tnl FLY-D|AC-D|RF-D|RB-D|AB-D|MQ-D|REL-D|SP-D|DUO-D|PD-D|CO-D> list
The shop's hours are 5 AM until 8 PM.
The shopkeeper will purchase: treasure map artifact parchment pen

Item (Type)
< 1 24> a map of Eastern Thera (map)
< 1 24> a map of Mierka V'Dramir's Pirate Cove (map)
< 1 12> a map of Arkham (map)
<15 276> a curved wooden pen (pen)
< 5 72> a thick piece of ecru parchment (parchment)

Jeril Dolansten tells you 'Nothing but the finest for my customers!'

“You can be a king or a street sweeper, but everybody dances with the Grim Reaper.”
―Robert Alton Harris

So out of the 6 maps he starts with, he only actually sells 3 of them. The Hamsah Map, the Western Thera map and one of the Eastern Thera maps are not typically for sale here. So when you bought those three maps, that is why they were not replaced in the shopkeeper inventory.

When you attempted to buy the second Eastern Thera map, it was replenished because that version of the map is sold by the shopkeeper.

There are two different versions of the map of Eastern Thera that are identical at face value but still different objects which is why the shopkeeper had and sold both versions.