Recovery of ISAM Table deletes all rows of that table

[Ioannis Ntelakis]

My company has an embedded Linux platform with mysql server/Client and a database of 8 ISAM tables. All those come in two versions.
The first one is a Mysql Server 5.0.32-Debian_7etch5 and the second a MYSQL Server v.5.5.31.
From these tables let's say 4 of them are used for select statements(read only-never change) and in the other 4 we user select/insert/update statements(read/write)
Both embedded systems are prone to crashes which is anticipated. The difference here is that when the tables are recovered the first version might lose 1-2 rows from tables that are read/write, and no rows are lost from the read only.
The second version will lose all data from the tables even from those that are read only.
Is there a reason to this? Does the option "myisam-recover=BACKUP" of the newer version in "/etc/mysql/my.cnf" play a part at that? The older server does not have such an option in the "my.cnf" file.