What do you know of the problem with Tefillin straps? I have just heard that the straps made in a certain place are probably Pasul because they were not made L’shmah.
In general, problems of Lishma in tanning leather fall into three categories. 1. The owner of the factory and workers are not trustworthy to do the process with proper intent - therefor it is necessary to buy from a dealer who has ascertained that his supplier is trustworthy. 2. Non Jews work in the factory, and care must be taken that Jews perform the proper parts of the process. Again, rabbinic supervision is advisable, many factories no longer use non Jewish workers (besides from the security factors.) 3. If the tanning is done in the type of vats that drain and replace the tanning mixture there is a problem of the Lishma of macines operated by a Jew (similar to Machine Matzot).