Hey Ari,
It looks like this is an Account field you're trying to write to. Marketo by default does not write to account level fields, so what's probably happening is that the change is pushed up to SFDC from MArketo, then the account's systemmodstamp is updated in SFDC and the change is reverted on the Marketo side since it was never made in SFDC. There are two primary options you have here: First, use a different lead/contact level field instead of an account level field, so that the changes are synched up to SFDC properly. Second, you can have Marketo Support enable account-level writing for you. I do not advise option two unless you have Field-Level Security in SFDC and have blocked writing to all fields which you do not want Marketo to update. This option can cause many problems if it is not thought through, as one contact filling out Company Name in a form can erroneously update the account name for all associated contacts.
.png)