IEEE 802.15.4 has become the de facto standard for low-power wireless systems in Industrial Internet of Things (IIoT) applications. Time Slotted Channel Hopping (TSCH) is used in the O-QPSK PHY version to improve reliability and enhance resistance to external interference. In this work, we introduce a MAC layer-based Forward Error Correction (FEC) scheme that remains compliant with the standard while being lightweight, due to its use of multiple smaller component codes, which results in low decoding complexity. This scheme is particularly suited for sensitive applications that seek to improve packet delivery ratio (PDR) at the cost of a lower information rate. We explore Reed-Solomon codes as component codes, analyzing the scheme's efficiency from a power consumption standpoint and its effectiveness in correcting erroneous packets. Testbed experiments demonstrate a significant boost in reliability, with the scheme typically recovering from 50% of all erroneous packets, though at a reduced information rate of 60%. Additionally, we highlight the benefits of adaptively adjusting the code rate across channels during runtime, as error patterns can vary not only over time but also depending on the channel.